Does this truck have a stick or an automatic?
If it is a manual transmission you probably have something like 3.72:1 or 4.11:1 differential gears. Swapping those out for 3.42:1 gears would make a good improvement out on the hiway. Most of these old chevy trucks are geared so you can pull a house off its foundation, but you can't cruise at 70 and get decent gas milage.
As I mentioned above rings and bearings are usually a good idea in these old motors, but if it doesn't smoke or knock and has decent compresion you may be okay for quite a while without them. In that case two of the easiest and cheapest improvements would be a small 4 barrel carburetor and dual exhaust. You can have your single exhaust converted to dual at any muffler shop without buying headers. It's cheap. However, you won't get the maximum benefit of improved carburetion and exhaust without better ( more performance oriented ) heads.
You say you are not a "gearhead" so let me put this in simple terms. The following items represent "paths to power."
Carburetor,
intake manifold,
camshaft and valve train,
compression,
ignition,
exhaust.
All these "paths to power" have to be more or less capatible to derive real benefit. You can put a nice edlebrock four barrel and an aluminum hi rise manifold on your stock engine, but just like you can't suck a bowling ball through a soda straw pouring extra gas in won't do much good unless you do somthing about those little bitty intake valves. Bigger intake valves means there's more going in, and so there is more that needs to get out, et.
At the very least I think in order to be happy you need to do the following:
4 barrel carb and manifold;
194 or 202 heads off an old 327;
mild performance camshaft;
dual exhaust with glass packs or turbo mufflers;
and while you're at it go ahead and replace the timing chain and gears.
You'll have it apart anyway when you're doing the rest of the work.
This would be an excellent project for a "NonGearHead" to make his bones and become an official member of our "brotherhood of the busted knuckle."
Good Luck,
Boo
