Y Block Flywheel question ?????????

I am putting a ford 4 speed behind my 256 merc and I have a flywheel off an early sixties 292. Are both motors balanced the same? I know the flywheel will bolt on but I dont want to have a vibrating piece of shit when I am done. By the way I have the 54 merc o matic if anyone wants it unknown condition but its free (as in no $) but must be picked up here. Thanks

 

The 54 239/256 are internally balanced, the rest are external. Flywheels come in 10 and 11" flavors and are interchangable on all engines however 54-6 Merc used a different tooth count I believe.