I would encourage you to run the flat 6. Search that auction site for a dual carb/split exhaust one. There are 2 on there now. One of them being a vintage Nicson with 2 Rochesters. The other is a new Offy which are still being produced.
I used to run just a straight pipe on my Chevy 6's. Or a Smitty for that old school sound. Definatley different that what every one else's sounds like.
Lots of carb options and as OldIron says the Strombergs would be nice. Plus if you have the cash you can buy them new... But my preference is to get an original and rebuild it as everything you need is available.
Another option is to run 2 but block one off. Many oldtimers did that as well with an otherwise stock engine.
Have fun.
Torchie.