I am installing a new engine in my 1985 f150 with an engine out of a 1981 f150 both are 300 6 cylinders. I was wondering if there were any differences between the years and what they were. If there is any modifications that I need to make.

 

Not that I can remember both are carbed so it should be pretty straight forward

again to the best of my memory.

 

Depends on the GVW and emissions systems of the two trucks. I know they played around with the compression ratio and cam timing in those years-
You'd probably get better answers from the six cylinder forum, though.