[Lynn Eades]

Some extra cubes give some low end gain. better breathing is for the higher end of the rpm range, and is not what you'll want. Save that one for your hot rod.
Being able to turn the thing, and get it rolling is where the problems lay.
Not much point in making it breath better (stainless manifolds, port job, cam etc.) wont help if its still restricted at the exhaust elbows.(and what else are you going to mod?)
The truck cam is probably as good as it gets, as cams go. The adjustable tappets will work with std cams, and the extra cost here is somewhat offset by the extra labour costs of the standard setup.
With an oversize set of pistons to increase the cubes, I'd say the last two posts have completely covered what is nessesary, for a great performing carrier power unit.
As with any motor job, just do it all well. (and yes Rich you do have to drill the block to use adjustable tappets, but it is also easy to make a minor adjustment later)