Wayne,
Sorry I took so long to see this. I've rebuilt a few of these Bartons, and my favorite is the U-40, which is what's on my '40 Chevy. The "A" in "UA" refers to a pump that has the heating/cooling jacket around the front of the impeller, to prevent freezing in the winter. The "U"s didn't have that jacket, as it was a later development.
As for the drive shaft: The EASIEST solution is to replace the belt with a link-type belt, which bypasses the tremendous hassle of removing - or at least tilting - the pump to get the drive shaft out. When my fan belt broke the year I got my truck, I purchased a suitable width link belt from Grainger. They're awkward to size - removing and replacing the links takes tremendous finger dexterity - but it worked well. You will have to ignore the ever-present warnings in the catalogs that say "not for automotive use". I ran mine for months, until the engine went down for a rebuild. Fact is, early autos (and fire trucks!) used link style belts in the early days from the factory. As long as you get enough depth in the pulleys, without binding, it will do just what it's supposed to do. Frankly, the only danger is, if the link belt brakes, you lose your fan and generator - so the engine may overheat, which is how I figured out my belt had broken! If you are accustomed to keeping an eye on your guages, you will have an early warning that something is wrong.
OK, that's the easy answer: Here's the hard one. If you're hell-bent on getting a proper replacement belt on there, than you don't have any choice but to remove the pump. It's not actually as awful as it sounds, depending on your plumbing situation. The pump mounts to an upside-down triangle mounting plate with three big bolts, and has ears that rest on top of the mount. Disconnect the intake line from the booster tank, as well as the discharge line to the booster reel - both hopefully have unions somewhere in them, or at least a section of flex line.
If your primer is under the hood, disconnect the vacuum line going to the front top of the intake. And if your truck has an auxilliary cooler, you may have to unhook the water lines going to and from the pump to it. Not remove totally, just unhook.
Now - wrap a chain on an engine hoist around the pump or attached plumbing and snug it up before loosening the mounting bolts. Keep 2 things in mind:
1, Do NOT disturb in ANY WAY the mounting plate! This plate is what has been aligned when it was installed to keep the drive shaft in proper alignment to the engine. As long as it stays put, the pump will go right back to where it needs to be.
2, ALL you need to do is pull the pump forward enough to get the drive shaft loose, maybe 2 inches. If it's not the double-u-joint shaft like you say, it's the original - or an inservice replacement - style, which is called a 3-jaw clutch style, I think. Either end of the drive shaft has a round clutch with 3 "teeth" or jaws, which mate with the 3 teeth on the pump side, and pulley side, respectively. These jaws were designed to take up minute misalignments in the mounting, and allow for flexing, to an extent. When you look at it carefully, it's hard to feel it was a good design. The double-jointed shaft that replaced these was a far better idea.
I would do my best to mark each end of the shaft to maintain it's indexing, so it goes back right how it came out. There may be a radial spring within the jaws either or both ends - keep your eyes open, though we couldn't totally understand the point of these, and I'm not convinced they're necessary.
When you put the new belt on, you may consider putting a second belt around the shaft, and wiring it up somehow to the back of the pump or the grill or something, so you don't have to go through this whole process if the belt breaks again - a spare already in place.
I'll send you a Personal Message with my phone number so you can call me with any questions. I also have a digital manual with drawings that would probably help.
-Michael
