OK guys I'm done. I think it was a total success. I was fairly **** about true-ing it up, and constructed something similar to what you wrote but using cartridge bearings for the v-block. Had to plug the keyway with a wood to roll smoothly on the cartridge bearing "v-block". The stub shaft I need is only 3 inches, just enough to hold a browning hub. Using a 20" long section helped a lot. The runout on the remaining stub is "almost" imperceptible. The real test is with a pulley on it spinning @ 780 RPM but I think it is about 1 or 2 hundredths.
I just used my wire-feed welder (Miller Multimatic 200). The welding wire is pretty tough stuff, I think harder than 7018 but thats just a seat-of-the pants guess (from bending the wire, & cutting it, and making a guess comparing it to 7018 rod).
I ran the welder on a 5,000W generator (on 220v). I was surprised and disappointed that the 5000w, 10HP generator could not run the welder on the 3/8" or 5/16" (thickness settings), I had to use 1/4" or the generator would pull down. But even so, since all the welding was on one spot on the shaft, the whole weld area was very hot, orange hot, very 'evenly heated'. I think I was a little lucky that it didn't sag and didn't seem to warp upon cooldown.
Here's some pics of the alignment and welding contraption. I was able to turn the shaft with one hand, while welding with the other hand. It was dicey, but due to the high heat in the area, the welds flattened out, and required very little grinding.
The original shaft was 1 inch where it broke. This new shaft (1.25) is 2.4 times strength of 1" shaft so I'm pretty sure my weld will hold. Also a 1.375 bearing has to slide over the shaft (&weld) to get to its land.
