Ford Flywheel, flexplate and imbalance info
 

Here's a link to a site that has good info on the different flexplates and flywheels available on our engines, as well as some imbalance info:

Ford Flywheels and Flexplates

Looks like the link above no longer works. I'm leaving it because who knows--it may just be a "today" thing and it could work in the future. Maybe.

In the mean time, here is the information from a different source:

https://www.motortrend.com/how-to/16...-and-dampener/


SHORT VERSION:
SBF from '62 to '81 = 28 oz imbalance on the flywheel or flex plate
'82 and up 302/5.0 = 50 oz imbalance
351W = always 28 oz imbalance