I have always been partial to JBA. Quality construction, super thick flanges, and nickel plating. They do blue out quick though. I paid about $325 for mine, just for the headers, not the y-pipe. I think they want another $150 for the Y. Pretty much all my friends with chevys have them, one friend got edelbrocks, and took them off inside of a month, due to leaks. They help out the 4.3 alot...if you really want to feel some power, go to Crower and get a cam for it. They have really nice 4.3 grinds, and the vortec heads flow better than anything I have even seen on a stock chevy by far. We built a 4.3 that was putting 300hp to the ground, and all we did was change the cam, headers, 1.6 rockers, and put bigger injectors on it. Of course we did the usual cat back and fat intake as well. But 300 is not to hard to get out of them. =)
JBA is the only company who makes a header for the 96 and up 4.3 liter S10. One problem though, they will not work with any type of body lift. One of the primary tubes wrap around the steering column. Other than that they are a good header.