You needn't pay to buy and ship an exhaust manifold. There is no difference between exhaust manifolds used with the 2bbl setup and those used with the 1bbl setup. The runners and outlet are identically sized. The differences in exhaust manifold configuration are according to production year, not carburetor setup. The '73-up exhaust manifolds will accept the factory 2bbl choke thermostat, or —*better —*get a #1232
Electric choke kit which will bolt to any-year exhaust manifold (if you're using a '70-'72 exhaust manifold, it'll have an open stove hole instead of a cast pocket; make a blockoff plate and then the electric choke will bolt atop the plate).
Carbs - a properly-built, properly-tuned 273 or 318 carb can run very well on a slant-6. The primary incompatibility is the choke lever (different for slant-6 vs. V8 ), which can be worked around without much difficulty. The later BBDs with the raised-top float bowls have a step-up rod and jet system very much like that of the AFB, and with (IIRC) rods and jets interchangeable with AFB items. But:
1. You shouldn't need to do much of any rejetting unless you are operating the car at elevation substantially different from sea level, and
2. There's a rash of new "high top" and "low top" BBDs on eBay. They are Chinese copycat/counterfeit/"reproduction" carburetors. If you put one of these on your car, please also apply a warning sign on the outside of the car so I know to keep far, far away from it on the road.
3. The early carbs run well, too.
It's all down to carb condition more than anything. Y'want a good, cheap, new, readily-tunable 2bbl carb to put on your 2-barrel conversion? Get one of
these new Holley 2280s, originally built as service replacements for '74-'78 318s in trucks. The seller's dependable—I've been buying from him since well before the internet—and the carbs are nice. Holley jets are very easy to get. The carb's
new, not a "remanufactured" piece of trash. The choke and throttle shafts are Teflon-coated. There's an inbuilt throttle-return spring (as required on all new cars starting in '74) for greater safety. The choke lever issue exists, but again, it's not hard to work around; whether you're using an original type 2bbl choke thermostat or the electric choke kit you can easily just bend up a new choke pushrod from brass rod stock, to meet the V8 choke lever.
The Super Six kickdown has gotten tough and expensive to find, but you don't necessarily need it. See
this thread for kickdown options.
Air cleaner: if you haven't got A/C, any '66-up 2bbl small V8 air cleaner (273-318, not the ones for the bigger 2bbls on big V8s) will fit and work fine. If you have A/C, you have to have the special \6 2bbl air cleaner with the flat front to clear the compressor.
The shorter throttle cable for the 2bbl is available new as Pioneer #CA-8417 (for pre-'77 cars that have a round metal ferrule where the accelerator cable enters the firewall -- later cars with the square plastic ferrule use a different cable, also still available).
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Wyncote, eh? That's where I was born. Here's a pic of the house my folks brought me home to...and the car they brought me home in. You can see I got an early start on slant-6 A-bodies:
