Ypu have to use the later 6250 cating cam as used on the 250 engines. With them, the cam was reduced in size near the counterweights. All aftermarket, and all 200 engines made after about 1970 had this extra clearance cam. The block at the lower end of the bore 'skirt' will have to be notched to clear the angle of the rod.
If you are heroic, the Aussie or Argie 221 crank will bolt in, and then you'll have to grind the rods back at the rod bolts. The block at the sump slipt line may need a trim back, as 221 blocks were wider than 200 blocks.
Every part of the 221 and 250 blocks were different to the early 200's. They may have been cast and machined at the same factories as there 200 cube cousins, but the whole block is wider at the sump and cam. Unlike a 265 and say, a 350 or 400 Chev, or a 221 and 302 or 347 Ford, the blocks are physically larger than there short stroke brothers. That means a 200 will always needs some carefull work with an air operated die grinder so it clears the recipricating parts by at least 60 thou.
Don't worry, though. Aussies have been hacking up blocks and dropping 221 Ford cranks into little Holden 186 blocks, and they have to grind the stock rods right back, notch the block and cam, piston skirt and dodge the water galleries at the base of the piston skirt. Get it wrong, and they created 'elaborate sprinkler systems'.
My advice is to start with a stock deceased junked block and have the machine shop do an offest grind to 3.35" with 'some kind' of 1.90" journal, 5.00" tall rod with a 23 mm small end. (I don't see nay B16/18 series Honda rods working. The aftermarket US built Civic block has longer rods which will push the pistons out of the block.Similarly, the Datsan L20 or Nissan RB20E sixes from Fairlady Z/ Skyline/ Laurel/ Cefiro/ Holden Commodore won't work, the pin is too small. Mitsubishi 4G rods are either too narrow and too small at the big end and too thin at the little end for the 1.6 and 1.8 or 2.0 Sirius or Cyclone engines. The 1.85/2.0 or 2.6 Astron is too big. Same with the Toyota rods. Either too big or too small. 5" Pinto 2000 rods from 1970 to 1974 have a 24 mm pin and a 2.05" rod size, and are strong. You' have to weld the crank rather than just offset grind. There are SVO 5.0" 2000 cc rods with Falcon 200/250 23mm pins. All I'm saying is that its real complicated!)
Use the aftermarket 3.71" ACL pistons, 1.163" tall. Rod ratio can stay down at about 1.48:1.
A lot of effort for 9% more capacity, but it all hinges on finding the right rod
