The one forklift the lumberyard had used an old Continental engine, on gas, but the propane one was definitely a "foreign jobber." (Sorry, GM guy. Ignorance is bliss...)
My dad used to be the serviceman for a local propane company years ago, so the family had a couple of cars converted over. Boy, I'll tell you: when you run out of propane, it's like shutting off a switch. Good thing we all ran dual fuel!
It would seem that doing the adapting to run a gasser on spark-ignited diesel could get complicated quick. As lazy as I'm getting in my middle ages, I'd sure try to find a suitable swap. Just me, though...