In the circumstance that there is no specific "diesel" class ( as in trucks and streamliners etc) a diesel powered car MAY (my emphasis) "compete" ( as in good luck with that) in gasoline classes. (see 2.B Fuels, Event gasoline-last paragraph).
As far as vintage engines are concerned, I don't see a specific prohibition to diesel (may have missed) but as there are so many specific regulations with respect to what vintage parts are allowed and modifications, you might have trouble with that one as has been pointed out. Unless you can run it on diesel fuel (and make any power) with no structural changes. Pistons are not a problem but i'd guess everything else might be- uh three main bearings and splash lube in a 20-1 4 banger flat head no less. LOL.
Anyway, as has been stated, come see at the track, talk with folks, read the rule book a hundred times or so and innovate away. Have fun.
