Hi Guys,
Sorry to chip in so late, but the computers fixed now (I hope), so we're back in busness.
I like the idea of the 3/8th drive u/j Walter, it seems really feasable. As you say it's joining the bits together when welding is a problem.
I'm sure that a local garage would help out if you get all of the bits preped and ready for assembly.
On the other hand, if you used 12 mm solid rod for the inner column, you could grind or file the end square for it to fit one side of the u/j, and use a short extension with the square (male) end cut off, for the shaft which attaches to the Gear, Cog etc. These extensions are only 10 mm in diameter, so should easily be upto the job.
If you have a pillar drill, or access to one, you could drill the bits and use 'Rolled Pins' as I have done, and then fasten the bits together that way.
Instead of buying new Walter, try local 'Flea Markets' and 'Car Boot Sales', they might turn something up at a fraction of the cost.
I have asked Gary about the U/J's he had, and he can't remember where they came from, be it a previous employer (most likely), or where he works now, but he said that they sometimes have them in at his works, and they are generally changed for sturdier items, so he said he'll have a look around and see if he can find one or two, for spares for other projects, so you might strike lucky yet mate!!

Progress on the car has been almost nil, with having to sort out the computer (I felt like I'd lost a limb!), so now that it's running again, I gan get back into the workshop and make some progress!

As you can tell by my ramblings, I've missed the forum,
Keep Busy,
Regards,
Mark.