Find a tuner.
The fear regarding the 347 has to do with the old design where the pin intersected the lands....that's no longer the case. Modern 347's are as reliable as 331's.
If it's speed density, find a local Ford EFI tuner in your area, stay away from lumpy cams that create idle vacuum fluctuation, then mod the thing all you want...the tuner can tune it.
At the very least, I'd put a set of heads on it. I have a set of GT-40 irons that came off my '93 Lightning if you're interested. They're in as-pulled condition with 70K on them, assembled with valves, springs, etc. I went to a set of ported aluminum heads.
The other thing you should do is get rid of the truck efi intake and convert over to a Cobra or Explorer upper/lower intake. The tuner can turn off the need for the EGR and other stuff...this makes the conversion easier.
If you do want to go mass-air, take a look at a 1995 Ford 5.0L California Truck processor. BIO0 family. It's similar in pinout, controls the E4OD, and is commonly used in these kinds of swaps. I've converted several trucks over to this box with great success...but if wiring scares you, forget it...look at Fords Mass-Air conversion kits instead. As I said, as long as you don't go lumpy with the cam you can get a tuner to tune a speed density EFI setup and it will run perfectly.
Byron