UDP crank pulley makes a big difference. I recommend it along with a corresponding overdrive alternator pulley (to keep the alt running at the right RPMs), and the right-length serpentine belt to match. This is probably the best single bang-for-your-buck bolt on available.
A catback may help a bit. Headers may help as well, and porting/polishing the intake may improve things. No one of those things will do much of anything on its own, IMO, but as part of the big picture they are worth doing.
1.7:1 roller rockers are said to make a very noticable improvement. Morana's are the only true bolt-on-and-go option, but the Rogue roller rockers (stuffforyourranger.com) don't require too much work (tap the heads, set the preload for each lifter) and are a bit cheaper.
Oh yeah, check your throttle cable (search TC mod). Many times on older trucks it's preventing you from opening the throttle 100%.