with machine work and a good basic rebuild kit your budget is gone, also you will need the springs recomended for the cam. The parts you have will get you over 300hp, BUT those heads are pretty bad. If you can afford getting something better it would help but a good set of heads will probably run you about a grand on top of your $1500 budget. Proper machine work and good pistons, bearings, gaskets, etc are NOT cheap.
Also, most s10 swap headers are 1.5" primary size, those cant support much more than about 350hp, good 1 3/4" headers run about $500, and they'll support a little over 500hp.