You would have to mill off the existing flange (about 3/4") on the 6 speed bellhousing and weld on this one. Making an adapter plate which allows both the engne and 6 speed to bolt to the adapter appears to be impossible, unless you tilt over the 6 speed about 8 degrees, something I am not willing to do.
So, if you got one of these flanges, you would have to go through that process: (1) mill off flange, (2) get a 1UZ block and have the back end pointing straight up, (3) bolt flange to 1UZ, then (4) place tranny on top, centering the input shaft on the pilot bearing and lining up top and bottom with 1UZ, then (5) weld up the flange to the 6 speed.
The best possible scenario would be if someone offered a 6 speed bellhousing with the new flange on an exchange basis. I'm not sure I would want to do that, as I would have to keep an extra 6 speed (to align the flange before welding) just to do this. If I could find a broken 6 speed really cheap, I guess I would consider doing this. At that point, I'm not so sure how many people would want to spend $$ on the 6 speed anyway. Offering something like this would probably cost over $700 + core bellhousing. I'd rather sell just the flange for less and let the buyer take care of the welding.