I’m there with Doug, It won’t “just bolt in” Can you make it work? sure anything is possible. Jag IRS and IFS are extremely popular with the hot rodding crowd. Is it an easy fab? Nope.
Correct me if I’m wrong (people), the XJ40 Jaguar Sovereign 87-94 (US spec XJ6) uses the same IRS and the X300, which I believe would be a direct swap. Though if you come across one with the V12. I’d dump the '97 and put effort into the XJ40. That’s just me though.