The output yoke on mine is round & has 4 bolts. Bentley's shows it as a triangular flange with 3 bolts, his photo must be a carryover from his e28 or e34 manual. The bolts on mine have a round head with a flat on them & fit into the driveshaft side of the flange, & have a 15mm or 17mm locknut on the tranny side of the flange. I'm sure I just used a box end wrench on it. Would you have enough room to get a box end wrench on it if you grind it down a little thinner to clear? Don't worry about applying too much torque, it should be good for many hundreds of ft-lbs.