Hi connor19,
welcome.
i just can help you with the first 2 questions.
1. Dimensions
Shelby Cobra parts - at Cobra Restorers, Ltd. - you will find the blueprint of an 427 chassis here.
The drawings have some mistakes but its a good start.
A lot of people build their chassis based an the drawings.
or
https://www.chuckcobra.com/ - he has also drawings - but i am not familiar with them.
2. I do have a scan of the body and can help you with some details, but i never build one body.
I am sure its easier to buy one...
Paul