I had this problem on my E body.. I jacked the car up and put a block under a tire on one side and lowed the car down so the tire sat down on the block which prevented it from spinning. I then went to the other side and and slowly spun/jiggled the new axle I was installing until I felt it...
Flywheel from Brewers..
New OEM replacement flywheel to fit the LA based 360 cast crank engines used from 1971 through 1992. These do NOT work with the Magnum or crate engines.
-6 bolt crank flange
-130 tooth ring gear
-11.625” pressure plate bolt pattern for use with 10.5”-10.9” clutches...
I hope it works out for you; I watched them build out a 904 lockup for my transmission, it was amazing to see how little there really is inside of those...
My 72 340 was never that deep in the 12's, more like 12.8 - 13.1 with some ethyl, a thermoquad, headers and G 60's on the rear.
That is some sorcery going on there.