Rear cab panel replacement?

[dunce79]

I'm giving up trying to fix the window channel and other rotted areas of my 59 Big Window cab. I think I'll have a much better end product if I just replace the whole rear of the cab.

1. Anyone done this and can comment on how well the replacement fits?

2. Any tips/tricks?

3. How should I go about bracing up the inner structure? Was thinking some diagonal down legs from the middle section down to the floor and then 1-2 going across the cab.