1975 Model Year Cars - Must run on Regular with a cat.

I searched "1975" to see if anyone has a thread just for cars in 1975, none showed up so I'll start one. I only want cars from 1975 and ones that run on Regular Unleaded fuel with a catalytic converter installed.
Here's one I made:
Does anyone know why my engine's reliability is so low BTW?
Here's one I made:
I'm not exactly happy with it although that's more because I don't like inline 4s than anything else, I mean for this car to compete with the Corvette and to beat it on both the track and strip purely due to it's lightness. This particular variant is the most powerful making the same 165 horsepower as the base Corvette of the same year, there will be lesser versions running lower boast with better efficiency although I'm not sure if I'll be showing them.
Does anyone know why my engine's reliability is so low BTW?
I'm guessing it's to do with the boast as in previous builds you'd get a warning if you run more than 10 PSI with carbs, but that warning isn't showing anymore so it could be something else. If for some reason you do want to see the other variants once they're made, let me know and it will increase the chances of me showing them.