Careful now.

ITE rules are vary a lot by region. I'm not sure what the folks at NC region had in mind, but their rules appear more restrictive than most. They have also used the WDC region ITE rules for the 13-hour (this year they called those cars ITF). I don't believe an alternate fuel engine swap is currently allowed by either the NC or WDC regions. I don't see any reason they would not allow it if you ask, but I would strongly recommend running this by someone with authority before putting a lot of effort into the car. Don't just go by a tech inspector either, they would be a good resource for some issues, but have no authority over the rules if trouble comes up.

Diesel is allowed in certain cases, so I see no reason it would be banned in ITE/ITF. Anything more exotic is probably a non-starter.