Do you need Gears? remove the tranny and go direct drive from the flywheel to rearend. Don't some midget sprint cars run like that, have to be push started and you have 2 miles to get up to speed, that should knock off a lot of parasitic drag if allowed.
My 57 F100 is shortbed fleetside, can you just change beds?
How about an Aussie UTE body, similar to unibody but with car nose so better aerodynamics, would that fall in pickup class?

55 Vicky & customline
58 Rack Dump, 55 F350 yard truck, 57 F100
59 & 61 P 400's, 58 F100 custom cab, 69 F100, 79 F150, 82 F600 ramp truck, 90 mustang conv 7 up, 94 Mustang, Should I continue?