Nice score on the manifold, your going to port it or just a gasket match to the heads? For carbs use what your most familiar with - if that's carter/edelbrocks and you are going to buy new then the AVS2 would be worth a look.
I thought 1/2" was a bit much considering where the stock pickup sits, but that was the spec they gave. I called it good at 13/32" - those tubes are a bastard to bend!