I am going to be converting my '91 4.9L (300) six from E4OD to ZF 5-speed pretty soon. I have 2 flywheels, one from a 351 and one from a 302. Can I use one or either of these on my 300?

 

no, the 300-6 is zero imbalance. the 351w is 28oz, 302 is 50oz

 

Will need a balanced (zero) flywheel. Or the engine will vibrate.

 

OK, thanks for the info (impressive knowledge with the weights, KB). I will need to seek out a 300-specific flywheel then. Followup question: If I am looking at one that I am told is for a 300, will it have no weights on the back whereas the 351 and 302 will?

 

On the engine side of the fly wheel it should be same finish all around. A 302 and 351 flywheel will have Pie Section weights cast in the engine side.

44dwarf

 

You can hunt down the specific flywheel you need, or any any machine shop rebalance the 302/351 flywheels to zero. It's an easy job actually.

Just make sure the 302/351 flywheels fit nicely and line up on the 300 crank snout, otherwise its a waste of machine work. Though, the machine shop can weld the holes closed and redrill. I've done that before. That's a PITA but it does work just dandy.