Have a 73 nova with a 454 over .030 781 heads and th400. Im pretty heavy at about 280. So i wanted to look into coil overs but with my weight, bbc and 73 big azz bumpers. I was wondering whats a good starting point for spring rate. Plus im running 18s all the way around if that makes a difference. Found a good price for QA1 coils but the rate is 550.