Don, short version, a- mods are an open motor class,cast or aluminum heads with steal blocks. Any type of rear suspension, 4 link most popular. 8000 rpm chip. X-mod, 360 ci limit ..9 / 9 1/2 to 1 motors, open head but all cast with a 2 barrel carb. Rear suspension is a 3 link only and i believe a 7200rpm chip. Front suspensions and chassis are about equal. As i mentioned before some of these cars run well, cruces can get a couple who will run in top ten on a weekly show. Pat Carney qualified for the big show in cruces with his x-mod vs the open mods. If the main event were to slick up alittle these cars will be hard to beat, less power means less tire spin equals faster lap times. Should be a fun show if guys participate.