I think it is a question of how much do you want to spend.
There is a pleathra of efi systems out there.

Megasquirt is a mostly diy system that could be done for under 1k or so.

There is a mustang 5.0 injection swap people have done for mopars for whatever the yard will let you have it for.

Don't know if edlebrock finally started making one for sb or not, but as I recall, that was well north of 2k.

MPI vs TBI will again depend on how much you have to spend. Most MPI are still batch fired regardless of what they say. As you move up the food chain, they become bank fired. Then the higher dollar ones eventually actually are port fired. But based on what I have seen, you are talking about 4k vs the 1.5 k you linked to.

Also for TBI, holley makes a commander or something like that for about 500 less than what you linked to.

You could also swap out to a magnum and use the computer stuff from a dodge truck. There are a couple threads on that already.

Or you could get the redrilled, or magnum heads and intake, if you are stuck with using your old block.