Try Restoration Supply in CA. I think the Filling Station used to carry them as well. They will come straight and you will have to carefully research how to bend them. It is a little tricky.
The original drip rails were essentially 2 pieces. An aluminum base held on by a nail strip and a cover lock strip installed by using a 5" block of wood and a hammer that compresses the sides of the base strip and locks the two together. The service manual was VERY specific about the block. I doubt you will be able to exactly match the one on the other side so there is a good chance you will have to replace them both.
Absolutely, I have 3 '29s of various models. If there is anything else you are looking for hopefully we can steer you to someone who might have it. I genuinely do enjoy the creativity of certain rat rods, and would love to see some pictures of what you come up with.
Sorry, I was up in Vancouver and have not been on here for a little while. No, the only car in pieces is a roadster, and it does not use drip rails. Again at one point Restoration Supply in CA used to carry some that were similar. They have an online catalog. Another place to check is some of the model a suppliers. Ford used at least 2 body builders, one of which was Murray. It was an all wood body like our Chevrolet's.
Please let the forum know what you find. I am sure there are other people looking for some as well.