You can get one of 2 5 speed transmissions for that truck. Either a
Mazda M5OD-R1 out of another F150. they were a stock option in the 88-96
F150's with the 6cyl and the 302. should be a pretty much bolt in
affair. however they were a hydraulic clutch. not sure if that 85 is
hydraulic or linkage. i think 83/84 they switched to the hydraulic but
not sure.

the other tranny you could use is the heavy duty ZF-5 spd. these were in
the F250/350 trucks usually behind the 460/diesels. some did manage to
make it into the heavy GVW F150's but are hard to find and are super
expensive when you do. i have seen useable cores for these go on ebay
for around $400-600 with rebuilds running around $900-$1200

If your not hauling and towing a whole lot the mazda 5spd will be fine.
they are everywhere and are dirt cheap usually. check out
www.novak-adapt.com for some good tranny identification info.

Jason