Roush Transmission?????

With the power numbers you are anticipating it would last till you take it to the track and the car hooks. The axles are weak and the trans isn't the strongest. The weight you are trying to move is the downside with the stock tranny. It just depends on how hard you drive it. If you plan on going to the track much and running the car hard I would upgrade to a tremec 3550 or TKO. Do not buy a TKO 500 or TKO 600. They have issues just above 6K rpms. If you already have the rear end upgraded then great. It isn't a cure all though. With the weight of our cars I have broken moser axles and auburn pro's on hard launches.