I made a few statements about sleaving old 200 and 250 engine blocks. You guys stateside might like to contemplate this if you are bored!
Option 1. The best option I can think of is GM 4200 Atlas LL8 pistons. They are 3.66", and have rods with 2.25" pins. There are 5.7" rods, in a 9 inch deck engine with a 4.05" stroke, and 1.335" decks. It would fit a 250 with 300 Ford rods and no mods asside from a cylinder sleave.
Option 2. The 200 could use these too, but with Ford OHC Pinto 2000 rods. These were popular Baja engines, and were made in Europe from 1969 untill 1988, but are available from Scatt or SVO. They are 4.96 to 5", but can be made to suit 4.905 by carefull close and grinding procedures. They have a 0.912" or 0.945" pin version, and the rods and Atlas Chevy pistons could be made to be 'friends' without too much effort. Early 2000 Pinto rods are very tough, and plentiful overseas.
(The 4.8 Chevy Gen 3 LR4 has a 3.779 bore x 3.27 stroke and 6.278 inch centre spacing rod, 1.335" tall pistons
The 5.3 Chevy Gen 3 LS4/LM7 has a 3.779 bore x 3.622 stroke and 6.098 inch centre spacing rod, 1.335" tall pistons
The 5.7 Gen 3 LS1 has a 3.893 bore x 3.622 stroke and 6.098 centre spacing rod, 1.335" tall pistons.
All Gen 3's have a 9.24" deck, 2.2" rods, so the pistons and rods won't fit a 250 block unless the crank is welded up).
Option 3 a. The US 250 has heaps of room for a welded stroker or good 300 six rods. On a wildly sleaved up 250, the 5.3 pistons with some bushed 300 I6 rods and a set of custom 3.88" steel liners would be possibe without too much outlay. 263 cubes.
Option 3 b. Weld the 250 crank, take stroke up to 3.985 with Gen 3 6.1" rods, and you've got 268 cubes.
Option 4 a . Stock 4.0 Falcon AU pistons, 1.163", 3.632" bore, 6.06" rods. These pistons would fit the US 250 with sleaves, but you'd have to run 6.375 Pontiac rods, bushed to suit.
Option 4 b The 4.0 pistons would fit the 200 with sleaves, and then you could use 5.09" 302 Ford conrods.
Option 5a. 250 sleaved. The 2.8 Cologne V6 3.66" Pistons have a 1.59" deck, and are tough. They have 0.945" pins, so might fit the stock 5.88" rods and fix the piston shortfall these engines are renown for.
Option 5b. 200 sleaved. The 2.8 Cologne V6 3.66" Pistons have a 1.59" deck, and are tough. They have 0.945" pins, so would need a spirolock and bush from a SBF to work. They should fit the stock 4.71" rods resized to 4.65".
Option 6. No sleave required, just a pristine block or 20 thou over 3.72" versions. These would use oversize +150 thou, 3.7" 5.0 piston used in the alloy 5.0 Cammer 4V crate engines, listed SVO part M-6007-T50EA. The pistons are 4.6 and 5.4 height, but can only be used with a rod about 6.35 " tall. On a 200, you could use the 2.0 Pinto (overseas its the common as mud Cortina/Sierra/Capri engine)
WARNING. Saving Iron for Environmental Reasons Rant follows:-
I favour sleaving any Windsor I6 block for a common and cheap modern piston and rod assembly from a later model Ford V6 or I6 or Chevy V8. Any 250 engine, especially the US 250, is an investment, and I can't think of a better way to eliminate the problems with thinwall cylinders than by using a 2.9 V6 3.66" piston on reamed out 5.88" forged steel rods and Diesel Ford 2.3 Transit engine liners which you can make locally for very little money. They are something like 3.78" in outside diameter, 93 mm internal, and cope with 21:1 compression ratios.
The other option is using 4.8 "Generation 4" pistons by Zoliner. Mate this with the GM liner, and its 6.1" conrod.
There is also the prospect of using the latest 1.21" tall 3.7" diameter 5.0 Modular SVO OHC piston, which is to be used in the comming 6.0 or 6.2 liter Modular V8 truck engines. You get the engine fully relinered to 3.88", and using a 90 thou thick liner should allow the 5.4 V8 conrods and the 5.0 modular piston to be.
These pistons have had millions spent on them by Ford and GM. Back in the late 90's, Ford and Chev had issues with warranties on cold piston slap in service. So they worked very hard with Zolliner to elimate it. Along with detonation reistant conrods and the brillant work on piston ring clearances, there isn't a better cast alloy piston around. It would be silly not to work out a price on doing an linered up 250 engine block, and eliminate the prospect of ever having to do an engine rebuild again. Linered-up engines are able to resist detonation better, and if the liner is thicker, they are stronger than a stock Ford cylinder wall.
Talk it over with your machinist.
Option 1. The best option I can think of is GM 4200 Atlas LL8 pistons. They are 3.66", and have rods with 2.25" pins. There are 5.7" rods, in a 9 inch deck engine with a 4.05" stroke, and 1.335" decks. It would fit a 250 with 300 Ford rods and no mods asside from a cylinder sleave.
Option 2. The 200 could use these too, but with Ford OHC Pinto 2000 rods. These were popular Baja engines, and were made in Europe from 1969 untill 1988, but are available from Scatt or SVO. They are 4.96 to 5", but can be made to suit 4.905 by carefull close and grinding procedures. They have a 0.912" or 0.945" pin version, and the rods and Atlas Chevy pistons could be made to be 'friends' without too much effort. Early 2000 Pinto rods are very tough, and plentiful overseas.
(The 4.8 Chevy Gen 3 LR4 has a 3.779 bore x 3.27 stroke and 6.278 inch centre spacing rod, 1.335" tall pistons
The 5.3 Chevy Gen 3 LS4/LM7 has a 3.779 bore x 3.622 stroke and 6.098 inch centre spacing rod, 1.335" tall pistons
The 5.7 Gen 3 LS1 has a 3.893 bore x 3.622 stroke and 6.098 centre spacing rod, 1.335" tall pistons.
All Gen 3's have a 9.24" deck, 2.2" rods, so the pistons and rods won't fit a 250 block unless the crank is welded up).
Option 3 a. The US 250 has heaps of room for a welded stroker or good 300 six rods. On a wildly sleaved up 250, the 5.3 pistons with some bushed 300 I6 rods and a set of custom 3.88" steel liners would be possibe without too much outlay. 263 cubes.
Option 3 b. Weld the 250 crank, take stroke up to 3.985 with Gen 3 6.1" rods, and you've got 268 cubes.
Option 4 a . Stock 4.0 Falcon AU pistons, 1.163", 3.632" bore, 6.06" rods. These pistons would fit the US 250 with sleaves, but you'd have to run 6.375 Pontiac rods, bushed to suit.
Option 4 b The 4.0 pistons would fit the 200 with sleaves, and then you could use 5.09" 302 Ford conrods.
Option 5a. 250 sleaved. The 2.8 Cologne V6 3.66" Pistons have a 1.59" deck, and are tough. They have 0.945" pins, so might fit the stock 5.88" rods and fix the piston shortfall these engines are renown for.
Option 5b. 200 sleaved. The 2.8 Cologne V6 3.66" Pistons have a 1.59" deck, and are tough. They have 0.945" pins, so would need a spirolock and bush from a SBF to work. They should fit the stock 4.71" rods resized to 4.65".
Option 6. No sleave required, just a pristine block or 20 thou over 3.72" versions. These would use oversize +150 thou, 3.7" 5.0 piston used in the alloy 5.0 Cammer 4V crate engines, listed SVO part M-6007-T50EA. The pistons are 4.6 and 5.4 height, but can only be used with a rod about 6.35 " tall. On a 200, you could use the 2.0 Pinto (overseas its the common as mud Cortina/Sierra/Capri engine)