You must maintain it properly. If modifications consist of improper maintenance, then they will be forbidden.
The installation of nitrous or twin turbochargers on your fox body won't be allowed, as it overstresses the OEM parts.
No problem. Start with a 1967-69 Valiant 100 2-door post car. Ideally, a slant six and manual shift. Get RBRE to built a near-exact clone of what Rick Ehrenberg runs, except for aluminum heads and larger header tubes. That should comfortably top 600hp. (With too-small headers and 50 year old iron heads, E-berg's bullet made 550hp on Ray Barton's dyno.)
Transmission is easy: much as I'd love a T56, it really doesn't fit without major surgery...so, Silver Sport's Tremec TKO 5-speed, probably the wide-ratio model. Pistol Grip shifter, please.
Rear end is even easier: any 1966-74 A-body 8.75" (E-berg actually bought his NEW from the parts counter in 65!) with 2.76 gears and TorSen limited slip. Use aftermarket axles to get the 4.5" lug circle to use "big car" brakes and actually be able to find wheels.
Suspension is also not hard, but that's because I benefit from 20+ years of E-berg's experience. Starting in back...
Super Stock leaf springs (two right-side springs) de-arched about an inch, urethane bushings and no pinion snubber.
HD Bilstein shocks with MP/Rancho/Just Suspension kicker shocks for wheelhop control.
In front...
Extensive reinforcement of all stress points on the front suspension and steering. Reinforce the unit body with subframe connectors and floorpan braces.
440 Dart torsion bars.
Fast-ratio (16:1) manual steering box.
11/16" C-body steering linkage.
HD Bilstein shocks.
Just Suspension HD swaybar, with Viper swaybar links.
Brake system is...really not that exotic...
10" rear drums with downsized (7/8", rather than 15/16") wheel cylinders, Mopar Value Line shoes. That's it.
Front is a little more complicated...but only a little.
Master Power Brakes repop disc spindles. (Or any 73-76 A-body spindles)
1976-78 police Monaco/Fury 12" HD rotors
PN 3880557 caliper mounting brackets and 70's B-body pin calipers (slider calipers can hang up)
HD carbon-metallic pads...only because the Mopar Value Line pads E-berg used were discontinued in the late 90s. (Yes, he ran roadcourses with Mopar Value Line brakes.)
Wilwood adjustable proportioning valve, no booster, lightweight master cylinder (1980 Aspen) with MP adjustable pushrod. DOT5 silicone fluid.