I'm glad you got some enjoyment/inspiration/maybe learning out of it.
I have considered a TBI swap. I really want fuel injection. The things stop me are:
Cost; I have no idea how I managed to pay for the transmission project but I cannot finance another project.
Downtime; I don't want to not drive the car while I do it (though especially with TBI I could keep driving it while the work is halfway done).
Time; I've got so much else on my plate.
Motivation; I'm so lazy I'm not doing the other more important stuff.
No garage to work in; so if I do feel motivated the weather/lack of daylight often stops me.
It's running pretty well; many of my complaints about the carburetor have faded though I'd still love fuel injection.
On that last point, I think what it needed more than cans of carb cleaner was just to be driven a lot. The choke behaves pretty well now. Idle is a little faster than I originally wanted but I've grown to appreciate it for tough uphill launches. It starts as easily as anything with a mechanical fuel pump can, though I may eventually add an external electric fuel pump even if I keep the carburetor.
For my engine, my research indicated that it may be easier to use SFI from a newer Buick 3.8 (or maybe an early GM corporate 3800, I don't remember now) than TBI, though TBI would probably be easier to do on most engines.
Rope-Pusher's a great guy, I don't know if I could have done it without his online help...but yeah, he is pretty wacky.
That Impala is the same platform as my car. I'm pretty sure they made some major changes between 1979 and 1980 but the important stuff for a manual transmission conversion (dash/clutch layout, for example) should be the same.
The choke may be electrically heated. Hey if your tires are tucked in the wheel wells then some skirts would be an idea to help the aero a little, classic bumpers sticking out at the ends and around the fenders! For better cooling speed up the water pump. Can't you take the ac belt off but leave it tied to the engine out of the way so you don't have to remove the outer belts? I bet the manual tranny is lighter than the automatic and if you don't need the back seat . . . There is probably close to 100 lbs there!
Oh and the idle was probably set for an automatic with a little tc load not a clutch so it may run a little higher than you like.
I'm not sure how I'd feel about wheel skirts but they are on a long list of things I may eventually mess around with. Long before I do that I need to replace the rotted-away bumper gap plastic fillers, there's big gaps that have to be aerodynamically awful.
Interesting idea with the water pump.
I'm happy with the A/C now. I fixed it so it works and I don't want to let it rot away again and leak, so I'm willing to invest the fuel that gets used when it comes on for defogging the windshield.
The manual tranny comes out about the same with its hefty 53 pound flywheel. Might be a little lighter.
Good point about idle being set for the automatic's TC load. In that case, given that the idle is only a little high, it might no longer be a troubleshooting matter, rather simply a matter of adjustment...that's when it's time to go ahead and turn the idle screw!
You do know that the end of the choke is adjustable, it rotates, once you loosen the three screws on the edge and that let's you get the choke and idle cam opening sooner or later or in your case opening all the way.