A few points to ponder while thinking of your upgrade. Two things have rescued the American V-8 from oblivion. The first was the overdrive transmission introduced in 1985 to improve gas mileage.
The benefit of an overdrive transmission is two fold. The first gear is lower than that found in a traditional three speed or a two speed. By making the first gear ratio a 2.74 or 3.06 to one it triples the engines torque to get the car rolling faster. By using a 0.30 or a 0.33 to one final drive ratio you cut by a third, the final cruise RPM there by saving gas and engine wear. Finally the use of a lock up converter eliminates the inefficiency of an automatic that used to constantly slip reducing parasitic drag by up to ten percent.
Here is a description of the various transmission options you have from Chevrolet:
The second big thing was EFI or Electronic Fuel Injection. It was put in place to reduce emissions as required by law. Now most old car guys balk at the idea of EFI under the hood of their early iron and I do not blame them. I am a carburetor guy myself and EFI is an anathema. But along with computers and fuel injectors came computer modeled heads and intake manifolds that maintain a high air speed without sharp bends that place the air fuel charge into the cylinder efficiently. That measured amount of fuel to air that was injected can now be mixed by the new heart shaped combustion chamber and burned cleanly. The unanticipated side benefit of a clean burn is more power.
From the efforts of millions of dollars in research and design work by hundreds of mechanical engineers at GM's motor division we have some of the best small block Chevy cylinder heads ever made by the factory. Ten to fifteen years ago not even the aftermarket could touch them in terms of making power at 0.450 inch of valve lift or below (where 85% of all cams are ground).
However lately the after market has caught up with their blatant copying (called reverse engineering by lawyers) of the features that these Vortec heads had to offer. Today you can buy an aftermarket head with the same "Quick Burn" heart shaped combustion chamber, the same tall thin intake ports of the "Vortec" head, and the same raised "D" shaped exhaust ports that Chevy invented and used on the ZZ4 350, without the 0.480 inch lift limitation of the stock head.
Cams have improved greatly to reflect the improvements made in heads (the two are complimentary and neither will work well if the one doesn't match the characteristics of the other). Starting in 1987 all Small Block Chevy engines were equipped with a roller cam. Prior to this a roller was an expensive race only component that drivers talked about as a status symbol at car shows. The addition of the roller changed the possibilities available to cam grinders. Lobes that where previously thought to be far to too aggressive became common place with the availability of roller tappets.
Because all production cars have used roller cams since the mid eighties the oil companies stopped adding metal supplements to motor oil (principally Zinc and Phosphate) that prevented wear when you had steel parts riding on cast iron. They were removed to save money and because there was a remote chance (if all the planets aligned and it took a bad bounce) of polluting the catalytic converter found on all cars since 1973. This is of concern to those who own old flat tappet equipped cars like yours because without DZZP in the oil your cam will quickly wear out and destroy the engine in the process (filling the motor with metal filings as a bad lifter becomes a hardened steel tool turning down the cast iron cam lobes as the cam rotates). Because of this you have to add DZZP to your oil at every oil change or convert over to a roller cam on your next cam purchase.