I have not tried converting a V6 to an I6, so this is speculation:
A 4.3L is ~262CI, so the overall displacement is similar. If I had to make a guess, I think it would run but pretty badly.
The injectors are batch fired, so the cylinder firing order would not matter for them. You could deal with the timing differences/firing order in the distributor (just use a traditional distributor with vacuum advance instead of the computer controlled one).
I expect the fuelling would be an issue with the lower compression and different cam profile. Given the torque/hp curve differences between a V6 and an I6, I also expect there to be enough differences in the details of how they need to he fueled to cause issues. I strongly suspect tuning would be necessary to make it run acceptably, let alone well.
Additionally, by the time you do the machine work etc to install the GM TBI on that engine you would likely have spent more money than a Sniper (Holley) unit costs and be running 30+ year older technology.
If your goal was to keep it all GM and be able to scrounge junkyard spares, that might be worth it to you. If your goal was an economy fuel injection build, that is probably not the best approach.
