I like the /BMMP idea... Sure, the Cd won't be great, but: you have a frame for attaching your roll cage, a full bed for holding batteries, water/intercooler/dry sump tanks, relative ease for swapping engines, and pretty
soft records. An extended cab Ranger would do all of that nicely. Run E all the way up through AA using Ford stuff. Lots of aftermarket support for mounting about any engine.