Here's what I found....cobbling under my shade tree. Back in the bad old days....I was a (rather successful) open-mod snowmobile drag racer because I'm such a tinkerer/detail freak. I had rigged up a fixture on bearings and v-blocks to balance reciprocating parts in the sled (drivers, idlers, etc...at 10K+ rpm balance is a BIG deal...) so I dug it out and re-engineered it to hold these flywheels.
According to my (homebrewed) setup....both flywheels were balanced "straight-up" Neither had a "heavy spot" so I just put it together. It should also be noted here that someone had been tampering with this car LONG before I got it.....upon disassembly I found orange silicone oozing outta the pan-to-block rail, two different kinds of flywheel-to-crank bolts (replaced 'em) and NO pilot bearing (so I replaced the input shaft bearing as insurance).
Not done by MB standards....but it's as smooth as silk (added the motor mount arms and shocks off a 5-cylinder since I had them laying here) and runs like a clock.
And it's CHEAP. One easy payment. You gotta like that.