Suspension & Interior

I have a 91 Silver. w 4.3ltr 5 spd. I am looking for a headliner for a standard cab, and looking top beef up the rear suspension. I read in another forum about 3/4 springs, will they bolt into a 1500?Right width? Truck has 160K and still running great. Also while I'm at it, what would be a good after-market exhaust that won't sound like a rice-burner? Thanks in advance.