The megasquirt is an option but you'll still need a bigger tbi unit and a better manifold.
I went with the holley 670 cfm tbi(bigger than a stock 454 tbi), projection 2 inch manifold(yes they sell vortech 2" manifolds) , bigger fuel pump, and a prominator for my 355. All that brand new costed me around 700 bucks and i can modify my fuel injection any way i want save different fuel maps and switch from one fuel map to the other with the flip of a switch... for example i can burn a smog fuel map(lean it out), a gas mileage map, etc., and switch from one to another with the turn of a switch.
This setup will support over 350 hp and tq max is probably up around 450 ft lbs. This is a good way to go if you want to be able to customize your FI but it takes alot of reading and you'll need a labtop.
Tpi is not my specialty but from what i hear the max power numbers are close to the tbi.