UBB Has the monoball housings too http://ubmachine.com/monoballhousings.html
I would suspect the monoball issues on the street would be the same as using heim joints - noisy, intolerant to dirt and more rapid wear. I have never used them however so I am just guessing.
I was thinking about the spindles being rare because if you weld a bolt in there and ever screw up that bolt, the spindle is probably junk.
I don't know the relative size of your stuff compared to the stock car stuff, but if you could convert your taper as you suggest to a more standard size, you would have a ton of options. My car uses the Chrysler screw in BJ's on both upper and lower and there are regular BJ options plus about a million options for longer and adjustable ones for fairly reasonable amounts.
You might be able to purchase the reamer for similiar money to paying someone to do them for you: https://www.lefthanderchassis.com/v2a/viewproduct_group.asp?idgroup=2513234
I guess this was just a lot of words to say I don't know of a toyota taper mono ball pin.