If you don't already have or plan to install a solid input shaft specifically for the non-lockup converter your question dosen't matter. You can't install a non lockup with a lockup input shaft. To answer the question, a lockup converter "locks-up" in OD to give you better gas mileage and theoretically makes the trans like a clutch activated setup. Non lock-up allows the converter to multiply torque in every gear including OD. 2800 stall converters on a stock motor will stall higher once you start doing work to the motor. So, after heads, cam, intake etc, that converter could then be stalling at 3300-3400. You're going to get real tired of that fast.
Rethink your plan so you don't buy parts twice and have double the labor costs. I've seen too many people without a plan wonder why their cars run like crap, and they spend twice what they need to.