I updated my 1989 Brendella with GPS speedometer, Stargazer PP. It works great at my level of skiing. PCM 351 runs awesome, just turned 1000 hours on the boat.
Do you REALLY need ZO? Do you REALLY want to yank a perfectly good engine to upgrade to a Zero Off
EFI compatible powerplant? It’s going to be very expensive, but if that’s what YOU want and the Hull is in great condition go for it! Probably won’t recoup the investment if/when you sell but in the meantime you have a great boat.