stalling out

Try some Rhoades lifters. i ran them in my 340 with the same cam. Before the lifters, it idles choppy at 1100 rpm, after Rhoades lifters it idles smoother at 800 than it did with standard lifters at 1100 rpm.

I agree, look for a vacuum problem. If you remove the intake, consider a set of Rhoades lifters, they work. You will get better idle, more vacuum at idle, and more low and mid range power without sacrificing your top end power.