Nicholas Spyrou

I own a vertical spit and I would like to know if I could make a beef shawarma using only beef and what cut of beef should I be using.I have tried pork and that went great with my customers. I have tried the beef using my own recipe which I used for the pork and added mustard powder and white wine vinegar, but I haven't quite got the marinade right it is missing that great flavour. Also I am experimenting with the beef cuts I have used silverside and brisket but I have found them too dry. I am now using the pony of beef and knuckle of beef. Any suggestions please help.