The stock computer will adapt to all kinds of modifications without any reprogramming. Only when you get into really wild heads/intake manifold/cam combinations is a custom tune or chip needed for smooth street performance.
The 70 MM MAF concerns me: there are a limited number of 70 MM Ford MAFs that match the stock computer's programing.
Only the F2VF-12B579-xxx sensor used with one of the above 70 MM housings will match the 5.0 Mustang's stock computer. Evidently the –A1A, -A2A, AA, etc. on the end of the part number is a minor variant that did not change the operating specs. You should be able to ignore it and have everything work good.
It will run fine, but a custom dyno tune can wring every possible HP out of that combo.
I've been to enough dyno tunes where i'm a firm beleiver than any mod requires a tune now.
Of course, it's not cost effective to add one mod and go get a tune, so i usually try to say get your mods to a decent level, and then go get an SCT chip and dyno tune. Then if you do any more mods later down the road, the chip can be reburned.