If you end up buying one from Brewers you need part # CF106R. Keep in mind that a lot of parts from manual trans slant six A-Bodies swap right over. The clutch linkage, torque shaft, clutch fork and boot, ballstud/bracket (had to shorten it), and even the flywheel bolts will work on a small block no problem. So the fork you need is in more than just small block A-Bodies with a 10.5" bellhousing. If someone is parting out a slant car with a manual trans you might be able to pick up a ton of stuff for not a ton of cash.
I'll just throw this in here because I know it gives a bunch of people problems.. if your crank isn't drilled for a pilot bushing just go to O'Reilly's and pick up a roller bearing, part # FC69907. Brewers carries these too but they're a $4 more plus shipping. It saved my bacon when the bushing wouldn't fit. Good luck on the swap, hope everything goes well!