I wouldn't build a car with anything less than a 1.75" x .134" cage... You can go 1.75" x .105" Chromeoly to save weight but 4-6pt
1.5" is generally what K, J, I class minimums are for ECTA events... we're talking 150mph (max) cars. You could do a bolt-in deal to
save weight while road racing and make it easier on the street... I believe Maximum Motorsports makes some bolt-in options for that
platform.
As for other safety stuff, 650rwhp in that car will make some speed... I'm guessing 175+... Which would require dual fire systems, a
parachute, racing seat, Hans device, etc. Those are some of the general ECTA requirements, not sure what Texas requires.