LA small block timing is suddenly way off
Did the outer ring of the damper slip?
That would mess with ya trying to set the timing, but it wouldn't run bad because of it.
I'm betting it jumped the chain (Especially if it was a plastic coated gear) and some evidence of this would be off white plasic bits in the oil pan.
Sometimes just draining the oil can make some of those bits come out so you can verify that is what the problem is.
Of course there are other ways also, like pulling a mechanical fuel pump and checking the chain slop, or see if it takes a bit of turn back and forth with the crank shaft and see how far it turns before the distributor rotor reacts.
( I know you know this 70aarcuda, I just posted for the OP) :-)
