There is a military generator for sale in London Ontario that uses a flathead military motor. This one is reported as being a low hours M38 engine. These originally had WW2 engines in them, so you'll want to have a look and see if it's actually an M38 engine as the seller reports, or a WW2 engine. Price is only $1000, so either way it is a bargain.
http://www.kijiji.ca/v-cars-other/lo...ationFlag=true
Edited to add: I noticed it has a data plate from the French army, so it is possibly a hotchkiss era engine. Unsure if that will be M38 or WW2 vintage.