TF 727 Push-button Output Hub Converting to U-Joints

Professor Fate said

So, what's wrong with simply turning down the 3-2-189's outside diameter to 3.94? Then you have it correctly centered in the output flange, you have the correct 3.25 bolt circle, and you have your preferred 1350 u-joints. Done deal.
I would NOT mill the lip off the drive flange and rely on the studs to center your driveshaft, unless you enjoy "mystery vibrations".
Early Valiant Barracuda Club - ball and trunion U-joint conversion

Click to expand...

Unfortunately, last year I saw the link you posted, but it has two issues in that it either has incorrect information or is for a smaller output flange. The yoke flange 2-2-349 that article lists has a bolt circle of 2.875" and an outside circle of 3.625, both far off the 727 output flanges I have of 3.25" and 3.94". It wouldn't bolt to the output flange, and if it did it would be able to walk around on the flange.

As for turning down the 3-2-189 from 4.5" to 3.94", the towers would be undercut by approx. 1/4" at the base, which may or may not be a structural problem. The machining would introduce a sharp 90° stress riser where the towers meet the base that could be a weak point. I guess I wouldn't know until it popped.