I had the same idea a while ago, but after searching the internet, and finding some ides that I didn’t like, I bit the bullet and bought a Safari Snorkel of ebay. Think it looks much nicer than many of the ‘homemade’ snorkels out there. And because your XJ is a 93, the snorkel is much cheaper that a >96. It also comes with instructions and plans, and after a few hours of graft, you have a fitted snorkel.
Worst part was hovering over the wing with a hole cutter and wondering if it’s a good idea or not!!! :(biglaugh):