Ian,
When I received my TC(or vice versa) it was missing the chassis cross member which holds up the rear of the engine/gearbox unit-among other things. I spent hours under a friend's TC making drawings of that piece to duplicate it. You are welcome to them if you decide to try making it yourself. I should add that I was fortunate enough to live next to a blacksmith who did the work for me. There is a drawing in the original TC owners manual of the entire chassis which might help. Let me know.
Otherwise, the company Dave listed certainly seems the more sane way to go. I'd be interested in knowing how much they charge.
Let's all raise a pint to Cecil
Michael DeRentz