Re:Shawarma / Gyros / Döner
Welcome aboard. While I haven't looked into this from the perspective of a food truck, I have from a wrap/sandwich station as an additional alternative to what we were serving. While it never made it to fruitiion, before any serious investment in a Kabob grill, a home rotiserrie will do for proofing recipes. Most will allow for the spit to stand on a vertical base when removed for loading, but it works great for slicing too afterwards. There's several Chinese knockoff vertical grills available from the foodservice equipment importers that deal with Canada. As for the meat, most of the recipes that I found consisted of blending your own ground lamb and spices even if lamb can be hard to find or marinating leg of lamb. One particular source of good information that's near a UK version of our Top Secret Recipes series of copycat recipes is a publication called, "The Takeaway Secret". It's a publication that's full of British fast food clone recipes the author has researched and collected. We made some of the Greek yogurt based and Indian sauces served with Pita salads and they were quite good and different. Regarding serving, Naan is becoming quite popular in the states during the past few years and found where flatbreads are sold. It's doable especially to a market that's never seen or tasted the real deal.
Wish you luck.