Do yourself a favor and figure out how to reproduce the hand throttle feature of the early MFI cars. I suspect you'll be happy that you did!
AFAIK, on the 72 and 73 cars it's fairly straightforward. On the earlier cars I think it provided raw fuel to the throttle bodies (a potential fire hazard) but I think in 72 it got somewhat safer.
Ther eare so many that understand MFI better than I do - sear fo "earlySman" or "Ulimate MFI".