deaver springs makes some good leaf springs for the back of rangers if you can flip the rear shackle...not sure if that would be "bending the rules" a bit far or not for you.
Autofab.com I belive has a rear spring set up that keeps the shackles like ford put them out.
both companys put out a good rear set of springs that help keep the rear end from bucking all over the place.
big part of it will be shocks, and valving too
I dont see any where is says you cant run rear shocks threw the bed on some hoops. run some good "race" shocks..kings ,saws,foa's etc.
for the front not much you can do with the rules. I would suggest running a set of forged beams vs the cast beams.stronger, lighter,and will bend instead of shear if you have a ohh shit moment.
depending on how hard you guy's run you may want to plate the beams also.
I would also plate on the radius arm ears also.
if your running like a corr truck youll want a higher spring rate than the jeep springs. totally diffrent spring rate to be honset.
shocks and a coil spring's with the right rate are going to make a big diffrence on a stock class trucks."lift" coil springs are going to be a hit and miss play with them kind of thing,if you want to try with them.
a bypass shock with the last tube closed off to work as a bumpstop could work
biggest hurtle is going to be getting some decent size tires under it that will clear under full bump with the wheels turned.cause you only going to be able to get abotu 2inches of hieght with out getting the camber and caster out of wack.....I see you can move the cab back,and you could tub the front firewall to clear some tires.31,32 or some 10.50 33's maybe.
wheel base, reg cab short vs extra cab is a driver prefence really.the reg cab short, its quick and nimble but like to "dance" vs the extra cab, will be a little more lazy but more stable.
FOA shocks are good shocks for the price, any other 2.5inch race shock, I say pick what brand you use by what kind of price you can get.
forget about the white body "lifted" shocks. procomps, ranchos, etc. they will fade quick, and you cant valve rebuild them anyhow.
28 spline 8.8's I would put a tight posi in rather than a locker or spool.less chance of breaking/striping a axle shaft. lets some of the shock of loading and unloading disapate threw the clutches/spiders.