T3he crossmenber you got will work, A 400 Turbo is what has a different crossmember. but you do have to change the 4 speed mounting plate for the Big Block. You can get the plate about anywhere (Heartbeat City, NPD,SS396.com,Tamraz,Ebay,ETC.) They are usually around 99$. You also have to change P\S Brackets and Pump.