The whole 'automatic transmission' is really a non-issue. Don't know if I've ever seen anybody run with one. In NEDiv, we've got an IT driver who races with full hand controls in an manual transmission, and even a one-armed Formula Ford driver (really). They seem to manage with a manual box just fine.
In NEDiv (northeast US) and CenDiv (north central US - think Ohio to Iowa), ITE is specifically restricted to cars that meet the rule book of some OTHER series (Pro Rally, PCA, old Firehawk cars, etc.), rather than a 'run-what-you-brung' class. Super Production (SPO & SPU) is for all the other weird stuff, with more stringent requirements for cage, on-board fire system and fuel cell. As you're not going to find a Jag XJS12 mit auto transmixer in anyone else's rule book, it's SPO and a manual transmission if you want to race it.
Dropping all sorts of big missiles into ITE is a REALLY bad idea.
This Jag XJS isn't light brown/cream colored, and is occasionally spotted at 'open track days' in the northeast, is it ?