you'd have to bore your pistons, but you have enough material in the sleeve to handle it. also, as i learned the hard way, the r50 and r60 have a different cam than the r75, so if you go with bigger jugs you'll need a cam as well. pretty sure i have another sitting around that would work for you.
as for the stuck piston, i'd want to work on it with the jug still against the block otherwise you'll be fighting the just moving all the time. if you can get the motor out and sit it on it's side you could put penetrating oil on top of the piston and let it soak. patience and heat will be your friend.
Originally Posted by lucky6600
I don't think the 60 barrels would take R75 pistons, right?