I realize this is an IT Forum, however the idea of racing the XJS 12 in IT just isn't a good one, both from a competitive and economics stance. I purpose built my XJS 350 and raced it in both Super Production and ASR (Mid-AM) for 7 years. I got a little help from TWR and Grp 44 on setup, and the modifications were challenging and expensive...suspension, rear end, T10 Tranny, Tilton clutch, custom fender flares, weight reduction, to name a few.
She was very competitive with the GT-1 Vette's, Mustangs and Camero's once we got her sorted out and certainly drew attention (some good-some bad lol).
I soloed her for a year before the conversion with the 12 and automatic and she was bulky and lacked the low end response to get through the corners efficiently. They also overheat and require a changeout to dual electric fans and trans cooler.
My first post so can't post the pic of her (admin rule)...sorry
Good luck