Good evening! We haven't used the BIG GM ones in a few years. as you know/see guys don't care for them b/c of the cramped firewall. It does take stock GM replacement parts if needed. I dont think i have a curve map or anything for that big version. the little pro billet ones are basically clones of the MSD's w/o the rev limit function. same springs, bushings, and tune kit as ships with the MSD's.