Yes, he found 2 of them, that was all he could locate. I got one truck going, I have another. At $80 a pop when and if they can be found it's time to look at other options.
The original yoke will only take the one ujoint. It's possible a machine shop could give you other options, but not easily or cheaply.
The yoke that takes the ball and trunion is just a flat flange. They can make a new drive shaft to fit it with modern $15 ujoints available everywhere. I know, I had one made for my 40 dodge sedan. Cost about $300, done forever.
What I might do is replace the yoke on the tranny, then put a higher geared axle, like a Dakota, then have a driveshaft made to fit that combo.
It sounds like the yoke swap has enough possibilities to look into it.