i think that you have some of your information wrong, the swirl port heads produced by GM were amoung the worst performing heads they ever produced. i think you want the vortec heads these are the best performing heads that GM ever produced, you would be looking for either the 906 or 062 heads castings. these would even help you with gas mileage as they have an extremely efficient burn chamber and take full advatage of all the fuel in the cylinders during combustion, and they can be had for a few hundred $.
above would be my strongest recomendation
next you mentioned 4.10's with 38" tires (without doing the math) that is about like running a 31" tire (most stock truck size tires) with about a 3.23 gear, it's a little small to me i would look more into a setof 4.56's or 4.88's but then again that would reduce you mpg's. with running the 4.10's i wouldn't look at a cam with any more than 212 advanced duration otherwise your bottem end will be soggy. and yes you have a hyd roller cam in it. personlly i would scrap the TBI/FI and go after a performer or RPM intake with either a 650 holley or if you can find a good 750 Q-jet then i would go after that, the trick is finding one still in decent condition cause to buy one brand new will you about 500.00 vs 250-300 for the holley.
above would be A sugestion as well, but really i am always in favor of rebuilding the motor before you put much money into it. here is a quote i've heard many times "you wouldn't build a castle on a foundation of sand"