You’d need a 1987 US pickup as a donor. You could swap everything on the TBI motor over to yours but it would be easier to just swap the motor over rather than swap the intake/distributor/heads etc. Find a 1987 donor truck, pull motor, the gas tanks with pumps/lines, wiring harnesses, ECM, everything, and then swap all that into your 1991 MX truck. You’ll be replacing a lot of connectors on those wiring harnesses, half of them at least will have the clips broke off. You’ll end up having to replace basically all the emissions/FI sensors and rebuilding the throttle body and having the injectors serviced or swap in a remanned set.
I’ve seen a few of the MX trucks before at local car shows, they’re around here in my area. Haven’t gotten up close and personal with any though other than just peeking under the hood and inside the cab. I’ve seen them with manual transmission, is that what you’ve got? If it’s an automatic, what kind of automatic? The reason I ask is that if you swap to TBI there’s different chips for the ECM based not only on what motor you have but what transmission as well.
I’ll tell you this, opinions vary but I LOVE the 350TBI in my truck. It took a while to sort it out after decades of use/neglect before I bought it but properly sorted out it is incredibly reliable. I mean rock-solid reliable. Starts the same whether it’s 20F outside or 100F. It just keeps on keepin’ on. It’s a lot of work for the swap though and there’s always aftermarket FI options out there like the Holley Sniper system plus as others have pointed out you can have that Q-jet carb rebuilt properly and it’ll run just fine. Good luck!
