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OP
We are trying to help you narrow this down ... there's a process.
A 454 damper is External balance and has a pronounced counterweight... here's a pic of a Pioneer pn DA4541 ... you can clearly see & feel the counterweight on the REAR of this damper
If it was my car I would bet that when the cam, intake and carb was done they screwed something up.
yep and I’m trying to pin point this issue without spending time and money on other things it could be. Guessed it was the balancer but was wrong. However it did need one.
whenever the damper/flywheel situation might seem to be satisfied ... then there'll exist the distinct possibility the numbers matching motor may have been built with a 427 / 396 crank ... both are internal balance and Both damper & flywheel are different than 454's.
Recently, a quite similar situation played out in long threads here CF C3 ... I recall the owner had a C3 BBC motor with mismatched part(s) around crank. ... IIRC he is in Florida, had his own lift in his commercial building & an adult son was helping him. Seems like his may've been a 427 but that wasn't certain for some time.