According to my shop manual the 86 302 EFI is a MAF system. I don't think the 85-86 302 came any other way?
In order to change the top end you would have to replace everything - The ECU and everything connected to it from O2 sensors to injectors.
For the kinds of mods you are looking at you are probably better off lurking in some of the Mustang forums.... And add a '0' to your budget or a lot of months of paychecks.
You would probably be better off buying a different truck in the first place.
The 350 is a bigger engine, 302 vs 350 (5.0L vs 5.7L) It's going to have more HP from the start.