Hi i just bought a 65 f100, guy said it had a 390 and 4 speed out of a fairlane, while trying to get a clutch for it i found out he was wrong. turns out it has a 68 428 with 66 390gt heads, and with FE's I've double checked every number, casting mark, webbing, pulled pan and i'm confident with what it has. My question is has anyone heard of doing this and if so for what purpose? Thanks
The parts on the FE are reasonably interchangeable between some of the different engine sizes so it does happen a bit and quite probably came from Ford as it is. Alot of the casting numbers are cast for the original intended use. So for instance those heads were cast originally for a 390gt but this would not stop Ford using them on another engine and they wouldn't change a casting number simply because they applied it to another engine unless it had some different cast or machine needed for it. Thats quite common. Casting numbers can be confusing because of this.
Someone else may have also done this because of an issue they had with the original heads or perhaps they thought there may be some performance adavntage from those.
Being that it may be a 428 and not a CJ it would more than likely have the 390 gt heads. If it were a CJ then I would be alarmed that it didn't have the C8OA 6090N heads. But just like big block said people change parts and the FE is versitile with many different interchangeable parts it's hard to know what you really have. A lot of research and resourcefulness is needed to find out what you have.
It may have a 390 flywheel or a 428 flywheel....is another way of IDing. But you have to remove it and look for the two extra tabs on the flywheel for it to be a 428 flywheel. And since the 428 is externally balanced and if it has that flywheel, you may have lucked out.
My guess is that it may be a rebuild and that's the way it was done.
Get all the casting numbers and date codes ...maybe we can help you decifer what you have.