Get a COMPLETE 96 to 2000 350 vortec engine. You can pick up a good condition engine for less than $800. Factory roller cam and vortec heads are worth 50hp over the earlier non roller engines (like you have). Add a set of headers to make another 25hp.
Add a little more cam, better intake, and a little head work to make 350hp/380ftlbs.
If you what to make serious power then would then freshen up the engine, add a mild cam, drop compression to 7.5 to 8:1 cr, and add a turbo. 10 psi of boost will make around 500hp 550ftlb of torque on a mild 350. Use your megasquirt with bigger injecters (2x bigger).