283 intake/exhaust combination questions

[rthuma]

I recently installed a re-manufactured 1962 283 in my 1954 pickup. I installed the cast iron intake manifold from the 1966 283 that I took out of it, along with a Rochester 2bbl carburetor that was on the truck when I bought it about a year ago. I had it dyno-tested and it generated 120 HP (@4400 rpm) and 186 ft-lbs torque (max @ 2,600 - 3,000 rpm).

It has the original CI rams-horn exhaust manifolds and a bolted together 2" OD pipe dual exhaust system without an x-pipe or h-pipe cross-connection. It is getting ~12.5 mpg around town and ~15.5 mpg highway.

The dynomometer guy suggested changing out the exhaust manifold to Corvette 2-1/2" CI manifolds and running 2-1/2" pipe/mufflers. He also suggested putting a 500 cfm carburetor on it. He thought these modifications would help the engine breathe better and improve the engine performance (more HP, not sure what he thought would happen to torque).

The intake manifold is set-up for a 2 bbl carburetor (small-spread bolt pattern), so I'd either have to put an adapter on it, or change it out to a 4-bbl manifold.

The engine power performance is fine for how I use it (every day driver). Better mileage performance would be nice. I have to do something to the exhaust, since one of the mufflers is pretty beaten-up.

Should I replace the exhaust system with larger exhaust manifolds and larger pipes?

Should I incorporate x-pipe or h-pipe cross-over?

Is it worth changing out the carburetor to 500 cfm?

If I do that, do I need to change the intake manifold, or can I use an adapter?

Does one change (intake or exhaust) necessitate the other?

Will either change have a bigger impact than the other?

Thoughts?