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

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