First off, awesome machine! Secondly, transformer welders are very simple machines, and as long as it produces output, it just as current as any modern machine, tapped outputs or not!
I have a Forney which has the same principle. They takes the taps off the transformers off of difffernt windings. The one I restored I used as a kid. It was in a shop that collapsed. It meant something to me so I blasted it and took it all apart and rebuilt it. I love it. My cousin a pipe welder welded 1/2 plate with it to attach a thumb! It worked great. I'll post some pics one of these days