Thanks to everyone that offered help. I caused the problem to begin with by forgetting to take the glow plus out of the head before dropping it off at the machine shop. Then they didn't keep them, so I couldn't look at one. From what I can gather it appears that NGK makes the glow plugs for Kubota because NGK was the only hit on a cross match and I couldn't find anyone other than kubota parts dealers that could even order the NGK glow plugs. I did find some brands that I've never heard of that claimed that they would work, but didn't want to take the risk just to save a few bucks. Ended up ordering them through local dealer. Nobody had them in stock.