I have 89 F150 w/300-6 without a head.However I do have a older head that is good.Will this older head fit on the newer motor?

 

I don't see why not, but do you know the condition of the deck and the bottom of the head? They might need be machined, it would be a good thing to check.

Not sure as well but i think I read something about the 240ci head having a smaller combustion chamber and helping make a bit more power, but I would want someone else to verify that.

 

I don't have first hand experience with it but I have read that all of the big block six heads will swap back and forth through all years. However, I do know that the efi head has a smaller combustion chamber about the same size as the 240. Putting a carb 300 head on an efi sorry block will lower the compression. The carb 300 head is 76cc, 240 head is 68cc, efi head is 68cc--all of those are +/- a couple cc because the casting consistency on them wasn't spot on always.

 

Thanks.I am going to port and polish along with good valve job...