I really like the FAST EZ EFI and that is what I am going with on my 408 Stroker. I like the idea of the self learning and self tuning. As already mentioned they sell the ECU as a "Retrofit" unit. I think using GM parts you could easily assemble what you need.

I started going down that road but in the end decided ton the EZ unit, for me, the convenience outweighed any small performance gain that might see over the multiport.