Ok, thanks guys. Looks like the P400 is the one I should go with since I have no usable core.
Sorry for the thread hijack. I might start my own once I get to tearing into mine to see what blew. I definitely will if I get a P400.
If you don't mind me asking, how much $$ do you have into this build?
Something just went in my 6.2/6.5 hybrid I built about 8 years ago. I found oil in the coolant after getting low oil pressure. Anyway, I am trying to decide between a rebuilt optimizer or P400 and how much I will save...