This is what I fitted to my Jag MK2 about 10 years ago and still going strong. I believe it has more features than when I bought mine. Hide modern speakers behind old Jaguar speaker grills, XJ40's are a good source of cheap parts as nobody wants them.
https://www.ebay.co.uk/itm/Retro-Sty...8AAOSwQItT6pl~
or for tightwads or people who have overspent on their build
https://www.ebay.co.uk/itm/Classical...0AAOSwwzhZSUy-