I've got a 1965 production M-20 with a Hurst competition - plus shifter, aluminum bell housing, flywheel, clutch and pressure plate, z-bar and springs available to convert your 64-67 chevelle to a 4-speed. You will need a pedal set and a pivot tab welded to the frame (if not already there) in order to complete this swap.
The transmission was re-built about 2 years ago using parts from Manchester Muncie, including new bearings, synchros, shift forks and sliders, and the oversized front bearing. It's got about 3000 miles on the rebuild, as do all of the parts. The shifter was rebuilt using all new spacer shims and bushings, and the combination shifts crisply. Flywheel was re-surfaced and has no visible damage or wear, ditto the pressure plate. I have a new throw out bearing and pilot bushing for your install, and a new-ish rear slip-collar as well if needed.
The transmission has the following issues:
the tail cone case has been welded in one place. It isn't a mounting ear, it's right in the middle of the case. Does not affect the operation of the trans as far as I can tell.
The shift linkages have been welded to size. They work fine, but you have to give a pretty good 'snap' to get out of reverse. I would recommend new linkages.
the front button, where the countershaft is seated, leaks a little bit of oil, or at least it had some oil on it when I took The trans out of the car. These frequently do this, although the shaft fit was correct when rebuilt.
There is an audible whirring when in neutral with the clutch out. I have been told that this is normal with muncies, that you are hearing the countershaft and its gears spinning In the case. I didn't have any insulation between the trans and my ears, So if you have a console or something, you probably won't hear it. I just want to disclose it so that someone doesn't buy this hoping for a totally silent gearbox and be disappointed.
I have the package on Craigslist for $1150, and its $1050 here for anyone with a chevelle or elky.
john
ps if you happen to have a bench seat, I have a very cool gooseneck shifter handle and ball to match that I'll sell for a hundred bucks.
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John B. 1966 Malibu Ragtop 327, Tremec 6-speed, 4.11 10-bolt posi. And ALWAYS a work in progress.