I THINK I KILLED THE 340

I assembled it for a mock up (no rings or piston clips installed yet) for checking bearing clearances and piston height. The rods are new. I know they still need to be checked. I am going to do some swapping and rechecking in the next hour. I measured the the piston to deck height myself inline with the pin and checking piston rock. Crank was not indexed. Stock forged. I am assuming based on the difference between the side to side more was taken off one side. I should be able to verify that by swapping some around. I understand production tolerances vary some. I can cut the tops myself at work. The valve relief dims are my bigger concern if I do this. You are correct about different pistons. What I have is time and a bit of knowledge, which is growing by the hour thanks to you guys. Money is the bigger issue if I have to spend I guess Ill have to. I already have the SM closed chambered heads. I was expecting such a large change in height. The reason I had it decked was for a good sealing surface for the new heads. It was a bit rough.
If money is the primary concern then just optimize what you have for sure. There were a lot of production 340s put out there that are further off speck than what you have.

I'd swap holes with that 040 proud piston and rod combo and see if you can get it close to the rest, get the heads and deck finished for cometic gaskets and let her rip.