I came across a rear disc brakes conversion kit from Speedway Motors, part #91031928, priced at $349.00. The concern I have is the kit is specifically for a 7.5" 10-bolt GM. I believe I read on this site or maybe elsewhere, the rear disc brakes kit will interchange between the GM 7.5 and 8.5 rears with c-clips. Any truth to this? Please provide your input. Thank you for your help