It sounds like a fast street car/cruiser. The low deck 512 with ~6.535 rods works great as a drag engine but probably wants bigger heads. The low deck 496 with 6.76" rods uses a short piston... light, fast revving but maybe not the best durability. That's what I'm running with Ed heads.

Either could be good but I'd suggest the RB with 4.125" stroke for your setup. It uses a slightly taller piston and should work well with the Ed heads. With block machining and piston selection it is pretty easy to build a zero deck engine. Matched up with a common gasket in the .038-.040 range you get perfect quench. You will need a dish piston to get CR in the pump gas range (low 10's to 11 depending on cam).

I would and did go flat tappet. Adapting the RB for roller is expensive and a bit tricky I think. A solid flat tappet will give great performance. Break in, high zinc oil and maybe EDM drilled lifters make it reliable. Your stroker won't need to spin much past 6000 so springs don't need to be crazy stiff.

I worked with Mike at Muscle Motors to get my rotating assembly, cam and heads speced out and matched up.