Re: what size
there is no reason that you could not extract the same amount of pwr out of a fuel inj moter as compared to a carbied motor, it all comes down to selecting the right combination of parts, as far as fuel is concerned you can get some pretty big injectors that can put in more fuel than what most street motors could probly handle. another point to add is that you have more control over your fuel delivery and thus (once tuned correctly) have the ideal a/f ratio that you desire throughout the whole rev range under what load.
i'm running a twEECer in my car and have the ability of turning off the addaptive learning if i want to have a hard core tune just for drags or dyno, and then a couple of different tunes for street use. as far as the type of meter to use, map relies on manifold pressure, and with a cam bigger than 280* duration this plays havoc with the manifold pressure, maf actually mesures the amount of air actually entering the motor and doesn't have any problems dealing with big cams.
blue66coupe have you had a look at the availibilty and styles of manifolds to suit the 302/351w's? there is a manifold to suit most applications, (as far as street driven cars are concerned) that produce really high #'s, with drivability and reliability.
as far as bang for your buck is concerend carby's are a great way to get pwr, but with todays emission std's it's a lot easier to go down the road of fuel inj.
std stroke, alloy heads, comp cam, tfs manifold, 75mm t/b, 70mm maf, 30lb inj, adj fuel press reg, twEECer