its bigblock torque that chews up alphas. Don't worry about tearing it up with an SBC. Even if you do, Just get an SEI aftermarket replacement. Around 1200 and it comes with a 3 year NOFAULT warranty. If you hit a rock and break it in half its covered.
If you redo the 350, 350 hp is easy. I would talk to Bob Madera. Tell him your compression and heads, he will tell you the cam, valvetrain and carb/intake to run to get your goals DEPENDABLY.With the alpha I would try and keep the RPM's below sat 5200 though. The cam selection is key to making power and not getting reversion while the valve train is key to letting it spin.