I'm slowly acquiring parts to build my 6.2 blazer. I am not going to do anything crazy. My plan was to do a valve job, head gaskets, 6.5 p.side exhaust manifold and turbo, 6.5 intake manifolds, crank the pump up, possibly 6.5 injectors and serpentine belt drive. A lot of parts swap over from what I'm gathering. Then just hammer on it to see how she holds up. I'd be ecstatic to put 2-250 horsepower to the ground.
Depending on what you're after out of the truck you may be money ahead to find a healthy 6.5 and swap it to a mechanical pump if it doesn't already have one. I am leaning more in this direction because I think a little more power can be squeezed out of a 6.5.
Depending on how plugged with soot your stock mufflers are you may see a bump in power by changing them. Straight pipes are LOUD