Yes, no guide plates with self-aligning rockers. And make sure the rockers contact only the valve stem tips, and not the retainers.
As for a Performer RPM Air Gap, I'd pass on the gimmick (and the cold weather warm-up issues) and get a good ol' 7101 Performer RPM. Or if you want to maximize torque in the mid-range, a Performer EPS Or better yet, the much newer-design Weiand 8120 Street Warrior. But, hey, it sounds like the open plenum manifold is working just fine for you.
Did you get rid of that Holley 80457, or convert it to dual inlet float bowls? And are you able to use the rear vacuum port on the manifold? A problem with Edelbrock manifolds is the rear port is somewhat obscured by a Holley float bowl.
Glad to see you got some nice heads. My 350 got new Vortecs four years ago, but if I had a do-over I'd go with conventional heads. No problems so far, but their thin castings are prone to crack if the engine is overheated -- apparently even slightly overheated. That's why the vast majority of used Vortecs have hairline cracks. Of course I learn this after buying the heads, manifold, valve covers, expensive intake gaskets, etc, etc.
