the 12G was a good old loader in its days. In the late 1970-1980 era ALLIS used a 24 volt alternator on all the construction equipment they built, loaders, dozers, graders, etc. Most were an industrial DELCO unit. You probalby dont need an industrial unit (more money). I think i would go to NAPA and ask them what they have for some of the lighter duty trucks these days. Some of the 2 to 5 ton trucks are 24 volt, as is all construction equipment. You could use something for CAT or IH, etc. I bet most of them are made by DELCO anyway. as for adaptability, no problem. YOu starter will be fine, diesel dont know the difference. Lights are already 24 volt. Switching + for - should not be a problem. Some alternators are not single wire, dont let that change your mind if it is a 3 wire. Might also try www.ibdozing.com and ask them guys were they get 24 volt stuff.