Electric chokes are the way to go if at all possible...
"Vacuum secondary" vs. "Manual secondary"
A "vacuum secondary" carburetor uses a vacuum signal from the engine to engage the 2 barrels of your carburetor that are not used during normal acceleration.
A "manual secondary" has linkage that "kicks in" the 2 barrels of your carburetor that are not used during normal acceleration.
The "vacuum secondary", I found, to be better on gas and give as good if not better power for a mild engine.
2 1/4" is the MAXIMUM size that I would recommend for your exhaust pipe/muffler size for a dual system.
Your headers, should you go that route should be either 1 1/2" or 1 5/8" as measured at the head... The "collector", which is the end of the header that connects to the exhaust will be about 3"... the "reducer" is the part that bolts on to the "collector" and reduces the size of the pipe to the desired exhaust size, which is where I recommend a size of 2 1/4" or smaller...
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