I can't say which is better but I can say that I used to drive a 55 chevy 235 with 2 single downdraft Stromberg single's on a Offy aluminum 2x1 manifold and it drove like a dream. Better gas mileage, smother running and could chirp the tires going into 2nd.gear. The 235 was a rebuilt shortblock which had a .030" overbore. I installed a MILD 3/4 regrind cam and the exhaust was kind of weird. The exhaust was the front 3 cyl. went into a Fenton type short cast iron header and the back 3 cyl. went through the back half of the stock exhaust manifold BUT it was cut in half just at the side where the front Fenton type header was and was capped shut with a small rectanglar 1/4" plate that was welded on. Thus this still gave me use of the stock carb heater box.(a definate pluss for a year around driver). Maybe not the most efficient set up as far as exhaust flow goes. But, at least, I had true duel exhaust and it did breath better and it help performance a lot.(and it had that lovely six banger kackle when I stomped it). The carbs that I used were 1 5/32" venturi Strombergs but I have tried to find more of them with NO LUCK at all.
This car was driven year around here in Illinois from 0 degrees to 90+. I had just one carb set up with a manual choke and I often drove the $hit out of it. Set the carbs just once and that was all. (no fuss) but I think I would have to contribute that to the simplicity and excelence of the older Strombergs.
You may be able to find some old Zenith carbs on e-bay once in awhile (if you out bid me) they also would be excellent. But dont go overboard on the venturi size. And remenber what ever fuel you shoot in HAS to have a good way out (exhaust)
or the extra carb won't do what it was designed to do. Keep all the components on the mild side and keep heat to the intake manifold and you will end up with a DAILY dependable long lasting driver. My vote would be the 2x1 and it has more of that killer look to it when you pop the hood to check the oil. ha!
Kind-a long,(i get carried away sometimes) but I hope this helps some. ~ ED
