GTD chassis

Apologies before I start but I'll ask anyway. I had a 40 30 odd years ago and I've been around a few at historic racing. My 17 year old lad, who has almost finished rebuilding a Caterham really wants to build one. We've started accumulating parts, and have half a set of Mk1 bodywork to repair. A friend has a gtd and we've got a spare rear upright to copy. Has anyone got any accurate drawings of the gtd chassis please? I'm a fabricator so it's not a pipedream. He is doing a machinest apprenticeship so he'll be able to make a lot of the parts required.
Feel free to pm me if more appropriate. Thanks in advance. Any help would be greatly appreciated.
Would you like to send a list with prices please. We'll probably not buy much more until I can get the chassis sorted though. Cheers Ed