Man o man, this is one of the primary ways I entertain myself.
Daily driver- Land Rover or Range Rover of the era that has the auto engage roll bars above 15mph. Add the auto engage roll bar feature to the rear. Replace stock spring setup with short stiff spring for bottom few inches and super soft coil over tender spring for top 3/4 travel. Reattach stock air bags in slightly different location (springs are in stock spot). Inflated bag you get high lift soft off road goodness with no roll bars. Deflated bag you get low riding stiffly sprung cornering UTE goodness with fat rollbars engaging over 15mph. Power to suit.
I have owned, or own, or have access to most of the parts for the following:
Challenge Silliness
Turbo 4.8 FC RX7 Big S400 turbo on Chevy 4.8 with LS6 cam/intake/pan backed by TH400 with moderate stall. 335/30/18 tires all around. Lots of spring, 200 shot.
Scoobaru Big S400 turbo on Chevy 4.8 with LS6 cam/intake/pan backed by 4wd 4l60e with astro awd transfer case in whatever AWD subaru chassis you can get cheap. Set engine back far enough to get a rear subie diff in front of the engine and use stock subie axles and hubs all around. 33/66 front rear torque split, decent weight distribution, and lots of go!
CrackKick Suzuki Sidekick/Geo Tracker body on shortened 2001 up 4wd V8 Ford Explorer/AWD Mountaineer chassis. Powered by (you guessed it) Big S400 turbo on Chevy 4.8 with LS6 cam/intake/pan backed by 4wd 4l60e with astro awd transfer case. Has front and rear 8.8 diffs, double a-arm suspension front and rear, weighs very little, width is perfect with stock box flares built into the factory design. Want 335's on that one as well.
ChittiCar CitiCar chassis with Miata subframes front and rear combined with 155lb 155hp GSXR 1000 motor/trans combo. Body panels replaced with diamond plate and windshield replaced with expanded metal mesh. Think Mad Max. Wheels stick out beyond body so it would have a serious side by side look.
Berkeley me! Combine the berkely shell with some sort of frame from either an ATV of a cast off FSAE car. (I really want that one with the sachs wankel). Use the GSXR motor for a sub 1k lb nut. Add A-mod style wings and go play.
Ooooh-Forgot this one:
Emodiata Stock Miata chassis. Chop frame rails a few inches to move the subframes up enough to get desired ride height with good stock geometry. Move desired engine back and to the right to needed location to get the weight distribution rear biased and balanced. Fiberglass front and rear clips, no windshield, appropriate shocks, bushings, brakes, etc... I think you could hit emod weight minimums and be reasonably competitive with a fairly simple build.