I think what he is asking is what it would take to get a Duramax to 700-800 hp so he can get rid of that cummins of his.
Depends on which model you go with. LBZ and LMM are pretty much the same power just the LBZ doesn't have emissions where the LMM has the dpf like your cummins had. You can make that kind of power with 40% over injectors and a S475 over stock twin set up along with manifolds and uppipes, downpipe, exhaust, EGT delete. Now your motor won't last very long at that power level. The pistons will be first to go at around 650+ rwhp although some have went higher, but a hole in the piston was the result. Forged bottom end, with twins, some socal heads, and I would think 40 over injectors at least, exhaust manifolds uppipes, downpipe, exhaust, lift pump and built tranny will safely get you to 750+ safely and easily.
I may be forgetting some things but I hope some of the vendors that really know can chim in and help you get the right answers your lookin for.