Doot - A fact alluded to but probably not really stated in this thread is that a new carburetor, a new intake, and a new exhaust manifold, regardless of what is used, is only going to give modest gains.
The cylinder head is the weak link in trying to promote performance gains.
There are many threads on these forums about the cylinder head bottle neck. There are some really talented folks on here that have tried on kinds of tricks to make the cylinder head productive, and failed. Use the search engine. This topic has really been beat to death, always with the same result.
So, options:
(1) Enjoy the truck as it was built, maybe add a little eye candy; but recognize the limitations.
(2) Drop in a different 6 (261, or 292 Chevy, or maybe a GMC).
(3) Throw caution (and capital) to the winds, and drop in a (horrors) SBC
Like Jerry mentioned, if your intake, carb, and exhaust are either missing or not usable, lots of original equipment stuff available for cheap. Maybe swap the Rochester for a Carter (about the same power, but better fuel economy and reliability.
Jon.
