Three-on-the-Tree with 273 4/bbl?

@SSVDP Thanks for the additional evidence!

I'm pretty confident now this will be an authentic variation, with the nearly invisible change to 4spd plus Gear Vendor OD, 8spd.
One more thing that would be exciting would be surfacing of an original car with three-on-the-tree and 273/4bbl still intact. Has to be in the unicorn field somewhere.

I'm not there yet, but when I get to it, I'm thinking of ways to improve the precision of the mechanism, like upgrading the pivots to adjustable ball/socket etc.