ive got an 86 with a front tank that no longer wishes to be a fuel tank. it had dual tanks origionally but the rear was all messed up so i removed it and the fuel lines but left the wiring harness.. just in case. so i can go with either. the valve that switched between tanks also took a crap so its no longer there. my question is should i replace the 16 gal. front , the 19 gal. rear, or go with the 38 gallon rear tank? which would be the best route to go.. any help would be great!!

 

If you get the 38 gallon you will have to relocated the spare tire and you will have to modify the sender for the larger tank.
If you do allot of 4x4 or off roading then you will also not have the 'skid plate' protecting the tank unless you modify something.

You might read this thread where this was discussed.
https://www.f150forum.com/f13/fuel-p...upgrade-48850/