Ken.
Your petrol tank cap looks fine, and it looks very much like the one I made for my B29, but it was smaller in diameter than the Mark ones.
Michael
I did make the brass part in my lathe, and also electro plated it in my Replica Chrome bath. Hovewer I had the piece of brass from a friend as I have none of proper diameter, and likewise I got the 2mm petrol proof gasketmaterial from him also. The blade spring (if that is the correct name) took I from the fractured cap.
Is the neck and throat of the T35 tank equal to the Mark V tank?
I could make one for you if you are not in a hurry, but I dont think my friend have more brass of that dimension and no more of the the gasket material. Do you have?
You are welcome t email me.
hoejmark