I drive a 1991 Scottdale, 1/2 ton, reg cab, V6 & 5-speed, factory gauges. So i appreciate the obvious extra effort you made.
Had the engine out of mine a few years ago. Oil pan pinholed. So i gave it the works. New Dorman Oil Pan, the used rocker covers came off a marine V6 from Las Vegas. So: new tin, new bearings, new timing set and a set of eBay, correct for 1991, reman heads out of Idaho for $128, shipped (what a steal). New Dorman exhaust manifolds. Lifters disassembled & cleaned individually, pistons & rings cleaned of carbon. It still has only 125K on the engine/truck. .003-.004" wear in the cylinders.
I looked at the Walker Exhaust Catalog. There were 2 sets of pipes available for the 1991 Chevy 350 V8. Single tailpipe or optional dual tailpipe with a 3" system before the muffler. Then i noticed that the V6 and V8 used the same crossover pipe. LOL
So, this V6 breathes through a stock 350 3" exhaust system with a BIG muffler and dual 2" tailpipes. Did i mention that the cat was eliminated with a custom-bent 3" pipe? A V6 that rumbles softly like a V8 through twice pipes
Nice job on your model!