What needs to be done to put 68 crank/rods/pistons in a 77 block. Rebalance to be safe? Piston height difference too far off?

The rotating assembly has no idea what the casting date on the block is. Piston height is the same as is everything else. Do whatever you would do if you were putting it back in the same block.

Ring height?

you'd wanna measure piston to wall clearance & might need to remove the ridge (a subject in itself) & mockup the main bearings & check journal clearance/end play & good chance you will be OK there but you cannot assume nothing & you want a solid foundation (long block) then any correctly selected add ons (intake/carb/ign/exhaust, will give you a spot on/kick azz engine with nothing left on the table. Mockup/measure & go from there.

Ok. I'm scrapping the idea of using my 68 block.

Borescoped the 77 and didn't see a ridge. I was going to run my 68 with a small pit and some ring ridge until I noticed a little more ridge on the front of the #1 cylinder. So be it.

You're seeing a fair amt of ridge on the 68 block? Any possibility in the cards of a bore/hone/new pistons/rings on the 68 block?

Maybe, just not any time soon. This was supposed to be a good running engine when I bought it. That isn’t what I wound up with, so my budget took a pretty good hit with that. Now I’m probably going to head/gasket/cam my 77 block with the 68’s guts for a decent runner instead of a decent year matching runner.

The ridge hasn’t been measured but it seems to be more pronounced at 7-11o’clock on cylinder #1 so I’m guessing they are all outta round.

Do you already have the pistons, rods and crankshaft out of the 68 block? Trying to drive them out past the ridge may break the ring lands off the pistons. I don't believe the pistons will come out of the bottom of the block. Be prepared to take the ridge out of the cylinders.

For cripes sake get that intended block to a qualified machine shop to get real world numbers instead of this guessing crap.

It is. I’m not seeing where there is any guessing of numbers, just a couple questions. Thanks for your help though.

Lotsa ridge is probably a good indicator of worn out ring grooves.... so IMO new pistons are in order