I ran 904's for years with great luck. Best move I made was going to a A-1 brake when I was running my 725 hp W7 motor. The T/A brake would every once in a while creep on me and the A-1 never did that. With the A-1 brake, we added a billet input shaft from A-1 and other than an additional clutch and good parts, it ran great This was in a 2650 Cuda running low nines. Also had the stock 2.45 gear set.