I applaud your effort!! I would also like to build a Super Beetle for ITC, as I am very familiar with these cars. I’ve owned my Cal-look 1971 Super Beetle sedan for over 15 years. A few years ago, all I needed was a body to build one, as I had TONS of stock leftover parts including a fresh engine, used trans and brake system. Alas, I never thought about an ITC Super Beetle and sold off all my spares.
The cars can be made to handle very well with very little work (stiffer front springs, lowered, wider tires, addition of rear sway bar). However, you will run into some competitive challenges with the current SCCA rules for this vehicle (see SCCA website for rules):
1. Drum brakes. Heat dissipation will probably be a challenge. I would petition the SCCA to let you run Karmann Ghia front disc brakes, as they really help the braking performance of the vehicle and are from the same time period (1971-era performance).
2. Engine power. The rules limit you to a 1585cc displacement, stock heads with minimum (1” depth) match-porting (no combustion chamber re-shaping), stock cam & flywheel and 7.5:1 compression.
3. Curb weight. The current SCCA minimum allowable weight for this vehicle is 2000 lbs. A stock 1971 Super Beetle weights 1835lbs.
My approach would be:
Suspension: TopLine lowered front struts, 10% stiffer springs and strut tower brace, adjusted torsion bars in rear, Koni dampers all around. Topline larger front sway bar and Sway-A-Way rear sway bar. Airspeed engine brace for additional support on engine and rear shock towers.
Brakes: use the best German brake hardware you can find.
Wheels & Tires: Run a set of 1973 Volkswagen Sport Beetle 15 X 5.5 wheels with the largest tires that will fit (probably 195/65R15).
Engine: Weber 32/36DFEV progressive carb, new 041 cylinder heads (largest stock intake ports), Gene Berg 3.5 quart deep sump for oil cooling, Gene Berg Achiever pulley, 1 3/8” equal length header exhaust. Valve cover breather system. Electric fuel pump. 1975+ VW/Bosch alternator for reliable electrical power.
Trans: 3.88:1 ring & pinion single-side cover transaxle.
Interior: Proper welded in cage, race seat, seat belts, tach, oil pressure, oil temp, cylinder head temp gauge.
Run the car for a season, get it sorted, then approach SCCA about the brakes, engine compression & weight issues. Most of all, HAVE FUN! Best of luck! Post pictures of your progress!