You are pushing it with the 2004R. Overfill and maybe add bigger boost valves. Of course the factory 3000 to 4000 rpm shifts also suck. My 88 had factory 3000 rpm full throttle shifts. Of course the stock 4L60E that came behind the LT1 was barely better in stock form and crappier when both trans are beefed up. As much as I don't care for the sbc or LS, at least it will have modern SEFI.