I don't the UFO style adapters too bad. The 2 that I have been using for a few years now seem perfectly fine to me.
Also, I use them in any of my laptops with that socket like my Duo's, 3400c, 1400c, wallstreets when I had them, lombard, clamshell when I had one, and my Pismo.
I did not even think to check the voltages but I did not think it would be a big deal...I could be wrong though.
To answer the original question...I think it should be OK to boot the G3 off the 1400c adapter. They all have the same Wattage
Laptop: Late 2006 2ghz Black, Pismo 400, 1400c x 3, 180, 170
Duo: 230, 280c, 2300c x 2, mini dock x 2, Duo Dock II
Desktop: LC, G4 Cube, IIfx, Umax C600, PM 8600, G4 1.4ghz DA, Mac Mini 2011 i7 2.5ghz