HELP! finding correct U-joint

Driving the split pin out... I always set the steering up centered, wheel straight ahead, puts the roll pin vertical to engine side of coupling and drive it out. I do have a long pin drift for the job though. The pin drives back in from top down too. I'm guessing your exhaust is in the way. LA is easy access, slant 6 is too easy access LOL
Anyway, in this centered position the box coupling has a small notch in its lower edge. Notch is in line with the master spline at steering wheel end of shaft. If this goes back together 180 degrees wrong the steering wheel lands upside down. Then you'll probably file away that master spline so the wheel slides on any which a way ( been there done that ).
If others members want to argue that some aftermarket U joint is a easier solution at whatever cost, I couldn't disagree. I never installed one of those. That original box coupling would need to come off regardless. Good luck