Two things. First, always trust your machinists observation. Double check with him what the galling point is. Second, what is the application? Is it forged rod and 200 six piston from Venolia, Wiesco, Ross or Sealed Power, SpeedPro or old TRW pistons? Its not uncommon for the basic forged piston to be a +56 thou over 3.68 application which was modeled off the odd ball 3.736" V6 Chev/ 4.3 liter 1978-1980/ 305 blank. So it may have been designed for reworking to another line reference. It was very common to fit these pistons in other engine applications. There are some really interesting Rover/Buick/Olds/Leyland/Holden sizes in this size range, they can be reworked to suit small Ford Sixes, and they are around in plentiful numbers if your machinist can network the suppliers. When they are used, they require lots of checking. Good American forged pistons like TRW won't be a problem, but when you start getting specialist, scratch made items, the machinist has to do a lot more dilligent work to avoid clearance problems. Some v8 forged pistons were slipper skirt designs with relief cuts which allow the piston to clear the crankshaft counterweights, but on an I6 application, the conrods are at a greater angle than on V8'S, and you have to relieve the skirts. Even a 255 or 305 based piston has a really good 1.70 to 1.63:1 rod ratio, but a the same piston in a 200 gives a poor 1.5:1 rod ratio, and the con rod is always angled out more on its journey from BDC to TDC.
If its a 300 with 240 rods or a long rod 250, sometimes you get parts which aren't compatible without relieving work. All changes from FoMoCo stock practice is a risk, and you should cross check like your doing before going to the next step.
Although long rod engines reduce rod angularity at maximum piston speed, con rod swaps can cause clearnace problems. When a set of long rods on the short rod 200 and 250, the pistons skirts can get close to touching on low deck pistons.
Its basically because the pistons we use are designed by Ford to suit the rod to stroke application. Its not uncommon to use a longer rod from a related inline Ford four or other I6. In Australia, when we put in a 6.00, 6.06, or 6.27" rods(such as rods from an I4 2.5 HSC, i6 OHC 1998-2012 ohc Falcon 4.0, or ohv log or xlow 71-87 3.3 Aussie Ford on the low deck aftermarket pistons for 250 engines, sometimes the rod and skirt clearances are too close, requiring clearancing with a linsher.
Just check it, and do the mods to clear it. Other Ford pistons we use for I6's, like the 255 4.2 1980-1982 piston, the 1984-1992 HSC 2.3 or 1986-1992 HSC2.5 have differences in deck, piston pin offset, chamber cc and sometimes show cracking in service, often in cylinder number one. We are still learning good engineering practice with an engine design which is over 53 years old.
