Not that I'm running DT, but I have fielded many questions about how DT works over the years:
The "engine swap allowed" changes nothing, nor clarifies.
Should have been:
1) OEM engine, OEM supercharging, is permitted without a quick change axle. Currently the A/DT, B/DT, D/DT records do not qualify as DT. They lacked engine swaps, non-OEM supercharging, or quick-changes as required by Gas Coupe.
2) Body may be from a truck that was originally gasoline. Tilt bodies permitted.
3) Engine does not have to be automotive. Marine engines allowed.
4) No American-made "gentleman's trucks", such as El Caminos and Ranchos, even if originally diesel powered, are permitted. Foreign-made models of similar design are permitted, whether gas or diesel originally.
5) Vertical exhaust is permitted/not-permitted.
6) Chop tops are permitted/not-permitted.
7) Factory 4WD/AWD must be removed or made inoperable.
These are the areas that have caused confusion. It's always been an Engine Swap Gas Coupe Class (except no El Caminos).