I would check on craigs list and get a COMPLETE 350 vortec engine from a 1996 to 2000 truck. These engine came with factory roller cams and vortec heads.
should be able to get one in good shape for less than $700. Then get an intake, 750 holley carb, long tube headers, and maybe a little more cam. should be able to make 350hp/400ftlbs and still maintain a near stock idle.