With all the photographic and dimensional data gathered, the next stage is to make sure that the shape does not alter once you start to remove wooden components. Firstly, the frame needs to be supported correctly so that it is not twisted. If you have the space and equipment, then transferring the frame to a wooden flatbed might be an option. Personally, I think this is risky unless you know what you are doing. I prefer to keep the frame securely bolted to the chassis until it is fully repaired. This approach also requires some care. The rear of the chassis can twist fairly easily, so make sure the car is on flat ground and that all the springs are settled (if the axles are still fitted - which I prefer since it keeps the chassis loaded roughly as it will be when finished). That is, leaf springs have a certain amount of static friction, so stand on each corner of the chassis and press it down. Then check by sight that there is no twist along the chassis' length.