340 Intake manifold recommendations

That sounds like the Comp Magnum cam that you have.

Keep the TQ!!!!

You haven't stated your goal [ just fun driving, drag racing etc ] because that should be a factor in choosing the intake. Single plane intakes are for higher rpm; also stock c'ter & smallish 340 cubes are limiting factors.
So a dual plane intake is probably best. The combo is in between the Performer & the Performer RPM. If more street oriented I would use the Perf. More spirited driving & trips to the strip, I would use the RPM.