Rather than shotgunning parts at the problem, which rarely works, why not try to diagnose what's actually wrong? A HEI distributor might be a good idea, but the one you're looking at isn't a drop-in fit. The 2.8 liter V6 distributor from the 81-82 S-10 needs some modifications to the shaft to drive the oil pump properly and fit into the stovebolt block at the right height, and the large diameter HEI from the 90 degree 3.8 liter V6 also needs some tweaking to fit right.
Start out by removing the original distributor and doing a complete disassembly, including the centrifugal advance system below the breaker plate. years of crud and congealed grease and sludge on the centrifugal weights and springs can definitely cause the symptoms you're experiencing. If necessary, find an old geezer mechanic who understands centrifugal/vacuum advance systems. Computer timing controls have dumbed down mechanics to the point that few "professionals" and almost no hobbyists are able to actually evaluate what's going on in a mechanical distributor.
Jerry
