I would start by looking for worn vacum line to modulator. Or the modulator could be bad. the modulator is located on the transmission which tells the transmission to shift when the vacum pulls a diaphragm inside the modulator a certain distance. some are adjustable with a flat blade screw i believe.
Brake - Shift Interlock
check your battery cables. could be old or just loose.
I believe it is 19 gallons ( U.S. ) front tank on your 1987 F150 long bed
on the side
There is a C clip that holds them on.
195 degrees F
I believe it is built into the altenator.
Check all the linkage from the transmission.
what are you wanting to take the transmission out completely or what?
under the dist. cap