I use a formula of (CID x .5 = head port volume) for a street motor, so 355 x .5 = 177.5 cc's. I'd choose the 180's.

You're using a dual plane manifold that will sign off at 5,500.
You're using a cam that will sign off at 5,500.
So, it makes no sense to use a carburetor that flows more than the motor can use. Being generous and saying the motor will ingest and use air and fuel at a 100% efficiency, 5500 x 355 divided by 3456 = 564 CFM. Being more realistic and saying the motor will operate at 90% efficiency, 5500 x 355 divided by 3456 x .9 = 508 CFM.

You can use a double pumper if you want to, but with gas prices being what they are and realizing that you are not building a world beater anyway, so it shouldn't need a double pumper would make me seriously consider a 600 with vacuum secondaries, no matter whose name is on the outside of the carb.