All these questions and I'm not feeling my best :brownbag :cry :uke: :wacko
No differences, you just paid more, and got that injector add on harness.
But I heard a rumor of some guy on this site that will convert a truck Speed Density harness to Mass Air using a mustang computer for a very comparable price. :toothless
I'm assuming your kit was $550ish new? $125 for a used computer, $50 for a MAF sensor, then what ever "deal" you work out with that stanger
No I don't have the details on my web site for piggy-backing computers.
Haven't sat down and sorted out the details yet. I could if there was a need. It's only time and money

You find the time or money to swap in that E4OD with the Mass Air, I could be persuaded to wire it up.
Can't stick with Speed Density, plan and simple. There is only 1 speed desnity computer than can be tuned with a chip to any usefull outcome. And it's not easy, and hates camshafts.
Not going to save any money with Speed Density in a stroker motor, all roads lead to 1989-93 Mustang Mass Air

How much money and time you spend to learn that determins your EFI IQ
Intake is another storry, I sugest the edelbrock performer for a stroker, maybe even a Trickflow