I think early to mid 2000s they have emissions. So not real sure before that. I would say it would probably have to be a pre huei motor. Sure someone will chime in that knows these motors better than I.
I've been looking around for info on the DT466E as I was looking to purchase one that I found at a good price for my first bus this was one of the better write-ups I came across while researching. Good Luck!