440 rebuild questions

Milling the block and heads to raise the compression sounds simple enough.........until you start to figure what actually has to be done to get everything to bolt back up correctly.

If your engine now has 90cc heads, -.120" deck (it's probably more than that) and a .020" thick gasket you would have about 8.25:1 compression. Reduce the head cc's to 80 and you have 8.9:1 compression. But, you have to mill the combustion chamber surface of the heads .042", the intake surface of the heads .052" and done correctly the top rails of the block (where the six 1/4" bolts hold the valley pan to the block) should be milled .071".

Mill the heads those .042" and the block .020" you'll have 9.25:1 compression but you have to mill the head's intake surface .076" and the block rails .105".

All the milling may mean your pushrods are now too long and you'll have to buy new pushrods.

Maybe better to leave the compression alone. If you want to increase the compression it's probably better to buy proper pistons and have the block bored to size. You may have to do that anyway if the bore is rusted bad enough where the piston was frozen.