New guy here needing help from you experts. I just got a 1977 F600 with hd330 engine that needs replacing. low compression on several cylinders with cyl 5 reading 0. I have found a 1978 391 within 2 hours of me that came out of a school bus with an automatic and is missing the flexplate/flywheel. I believe I read that these are balanced with weights on the flywheel, so does that mean it would vibrate itself to death if I put the 330 flywheel on the 391? This engine was an unexpected hurdle so I need to do this swap as cheap as possible. Thanks, Whit

 

Answer here:

https://www.ford-trucks.com/forums/1...e-choices.html

 

Let me know how your swap goes, I have a 330 that is in good shape but is really gutless and I have a buddy who has a HD 391, so although the truck is only seldom used it's tempting to do.