I'm in the process of rebuilding the engine on my Farmall M and I ordered a complete engine kit from Yesterday Tractor. Everything looks good. I went to drop the new sleeves in the block and they are loosey goosey. I measured the bore in the block and it is 4.25" The sleeve I pulled out has a piston size of 4.125" and the new one from the kit is 4.00". I bought the oversize kit knowing it is a direct drop in replacement. But based on the numbers it appears someone along the line had rebuilt this engine and had it bored out to accept Super M sleeves and pistons. I know its a 1939 M block. Tag on clutch housing and serial number stamped on block match. I guess my question is how common of a thing is it to see a bored out M block and if I order a Super M kit will the sleeves and pistons be the only thing different from the M kit? Look forward to the replies and thanks in advance.