Birdsong and a lot of the other keyboard warriors have given many of us a ton of misinformation. My suggestion is to call the company you got the axles from and talk to them. These day I try to stay away from yoob toob because of all of the BS that is put out there. Don't get me wrong, there is...
Boosted, I'm surprised you had troubles with the PTC converter. Kenny Ford and the group there are pretty sharp cookies. I know PTC recently changed hands, but I read that Kenny and about 98% of the crew are still there. I have 3 of their converters and I used them as needed with nary a problem.
I've had people call my Demon race car a Nova, even though it has a big Mopar M decal on each side of the hood scoop and Mopar spelled out on the rear quarter panels.
Folded like that will ruin the boot, 100%. On my cars, I use the long yoke and the seal pictured, there is 1/2", +/- 1/16" visible outside the boot. I have been running them like that on multiple cars for over 40 years, both on street cars and race cars.
Years ago I bought 3 slant 6 727 transmissions at an auction. I was told that they came out of baggage tugs at the airport, they all 3 had short input yokes in them, and they use 1350 u joints. I still have at least one of them somewhere in my parts storage.
Years back, Mr. Gasket and Hurst had what was called a "universal" three speed shifter. That is something you might look into if you can't find anything else.