350 rear wheel hp on stock block N/A would likely cost more than you'd like. On a healthy shortblock most HCI combo's will lay down anywhere from 260's to 290's depending on the combination of parts. Well selected combos...correct heads combined with a proper cam selection and intake can reach and pass the 300 mark when tuned properly. By tuned I'm saying maximizing A/F ratios and timing for optimum performance but will also extend the meaning to include the general condition of the engine and it's other components...sensors etc. Alot of factors go into what the output will be but you can find good proven combos like the TF kits, holley kits etc.