Intake manifold poll

LD4B is too small. LD340 would work, but finding one that hasn't been toyed with is tricky and they aren't getting any cheaper, when you do find one that is good enough to clean up.

For what it's worth the Action Plus/ Stealth is nearly identical. The runner pattern is the same, only the runners are a smidge longer and the Weiand has better casting uniformity... And they're available.

I voted Action plus, because you can run both square and spread bore carbs on it, if you ever do decide to play with a ThermoQuad.

You may give a Street Demon a run. Same gig, only it has a nice idle air bleed at the front to stabilize/ center the fuel in the intake plenum. RPM Air Gap is a good manifold, but totally unnecessary on an engine that won't give you heat trouble.