Too bad that stuff didn't fix the truck but looks like it needed done anyway. Vacuum gages are cheap, like $20. Timing is computer controlled so shouldn't be off unless someone removed the distributor and put it back wrong. You can do static timing but you need to pull a wire in the passenger underdash area first to take the computer out of the mix, then time, then reconnect. I've never done this so can't walk you though it. Could also be a worn out or broken distributor and probably some other stuff.
You could also visit these sites to get a wider audience for vehicle specific advice.
http://www.blazerforum.com/ - try engines and transmissions forum
http://www.s10forum.com/forum/ - try 262 c.i. (4.3L) V-6 forum