Flat cam lobe, what cam now

Call a cam company and see what can they recommend...... with those heads, bet it is smaller than a 590 lift cam.
Afterwards having to re install the inner spring maybe a pain in the asses, But pulling your motor to change cam is way, way more of a pain.
When you get it back together, set the crank at 20 degrees before (tdc Compression stroke) then point your rotor at #1. It will fire right off!!!!! And it MUST to save the cam.

Final note.
A cam that will flow with those heads will perform much better than a Too Big of a Cam.....just something to think about.