You could do it. But it would be a lot of work. Besides fuel rails, manifold, ECT you will need a distributor that will work with EECIV. You can buy the manifold, rails, and Dist from Mass-Floefi or other aftermarket EFI company.
You will also need to get a TwEEcer or other programmer to reprogram the EECIV to run a BBC. EECIV is a far better more powerful ECM than early GMs. But it is not adaptable enough to slap on a recalibrated MAF meeter and go from a 302 to a built 454 without a lot of re- programing
By the time you bought all the parts and a TwEEcer for $400 I think you would end up spending almost as much $$$ a if you bought the kit. Then there will be all that time and headaches spent adapting sensors, wiring, and tuning.
I think Mass-flo uses a GM MAF because it is big enough to fit right over the TB and not in a intake tube. Putting it right over the TB allows you to use a custom carb type aircleaner and have a nice clean look to the engine compartment without a bunch of wires and tubes.