I had a friend in high school with an S10 (didn't most of us have one of those friends in high school if we're under 40?). We tried Marine heads, Marine intakes, ported heads. We got started on an M90 conversion, scrapped that for a turbo and scrapped that after getting half the front end torn off to get the piping mocked up. Rich then tried his hand at porting the heads, and after 40hrs and 2 sets of heads...was no better off. Building a 4.3 to run 128mph can be done; but if you don't want to run the risk of being let down in terms of eating your budget, or marginal performance you may want to think twice.
Heres what I know. When I was your age, I had the money to do something once. So don't take what these guys are saying as a slam, its not. We want successful hotrodders. Also, the first thing you'll do after running 128mph is want to run 135. This is one of those laws of hot rodding.
Now after giving no hard information, heres some technical info.
You could put a stock LT1 in there and it would be cooler and more legal than a carb V8. It'd also have more room to grow than your maxed out 6'er. You can find a good running LT1 for less than a grand. You'll probably have to build a swap harness, but its not impossible, and there are several good how-to's on youtube for these kinds of things.
You'll also need to look at your trucks fuel requirements for this kind of power, I bet due to its age, it's marginal at best by now.
Personal experience; Im a member of the 3rd Gen camaro/firebird forums. There are a ton of guys over there who play with the 6 bangers and have a wealth of info. Most of em that dump money into them, come up short and kill the resale value of their daily driver. The smartest ones build a 2nd powerplant, and swap it in over a week in order to minimize down time. And then sell the car and buy a V8 one
You really want to do it? 3.23 gears and a bucket of nitrous oxide. This may or may not be legal in your area, and you'll probably run the TBI lean and melt it down. FYI a full bottle of nawss in your car is not legal in most areas, armed or not. As a young guy, they'll be itching to throw the book at you. Most of us here have 1st hand experience in that.
Stick around here, you'll be an asset for sure