Help me select a cam

You have headers, you do not need a cam with extra exh duration.
The Comp 270H Magnum would be the biggest I would use or the Isky 270 mega.
Have a set of factory lifters re-faced if you want to avoid lobe/lifter failure.

D. Vizard has three pages of cams ion his SBC book. Not one of them is dual pattern.

"If a true street engine is equipped with a modified head & free flow exh system, a single pattern cam will often be the best choice".

"On a purpose built street performance street motor, this extra blow down [ extended exh duration ] can cut mileage & low end tq by as much as 5% - sometimes more".