Bring a Trailer has the highest prices you can find. They keep all their sales on record. If I were you, I would go through the last year's worth, sold / unsold, enter them in a spread sheet and see what you find. I would look to see how non-original / hot rod versions fare on price.
https://bringatrailer.com/jaguar/xke-series-1/
I thought the Jag people were purists, but there was a stunning restomod with a FORD engine
that sold for a LOT of money. I am not a jag guy, but it pained me to see that choice.
https://bringatrailer.com/listing/1964-jaguar-xke-coupe-8/
This car is on my bucket list. It looks like it is taking off into unattainable territory.
G