How about the aforementioned flatbed,a set of front hubs from a 1 ton,a later rear with 3.73 gears,budd wheels(alloys if you can swing it),a Saginaw 4 speed with an overdrive installed,and a built 302 GMC six. Maybe twin stacks.It'd be cool,useful,fun and you would never see another truck like yours. That's how I'd do it...
Speed

1954 GMC 350
1957 GMC 1/2 ton
1962 Chevy C-30
1952 Chevy 6400 dump bed project truck
'98 Harley FLSTC
'66 Pontiac Catalina
'76 Chevy 1 ton Duallie
'84 Bronco II
'78 Dodge W-200
'81 Toyota 4X4 truck