Will a 1977 f150 body fit on a 1986 f150 frame?

Yes and no ......the frame on the 86 is wider ud have to drill new holes in the 77 body for it fit and make different mounts for the doghouse etc alot of hassle but its always possible if I remember right the 80s frames were 6 inches wider cause we tried to put a 88 cab and motor on a 76 highboy frame and it was to much pain so we got a 95 frame its backward from what your doing maybe find a older truck frame close to your year i do believe the 80s rangers had a similar frame width but it wont be as strongly built in my opinion