I couldn't agree with Steve and Dave more. I did a full resto and mods to concourse standards (comparable to Steve Healey 3) on an XK 140 in 1983 It took me 3 years, and I had a great deal of help from Jaguar factory, not only in expertise, but in locating some rare parts from their obsolete stores. It still completely took over my life to the detriment of my young family, much better to buy a fully fettled example ,enjoy driving it and play around with the detail.
SteveH