I just busted the spider gears in the carrier of my 7 1/4" axle. It's behind a 3000 lb. '74 Dart with a mild 318(.440 cam, 600 carb and duals)and a built tranny(2500 stall, B.W. clutches, kevlar bands, a shift kit, koleen steels). I'm thinking of getting a 3.90 gearset and a spool if i can find...