cage builder map. What type of car are you planning on building? Oftentimes there's a prepped one in need of updating, or even ready to go, for less then the cost of the cage and suspension in the forums. Welcome to the madness.
Wouldn't worry too much about where the builder is. If you can't get the car to/from them, you can't get it to/from a rally either. Pick a builder you're comfortable with, gives you a good price, and most importantly - you two are on the same page as to what to do and how to do it.
If it's a ways off, it's a good time to start talking to them. A lot of those guys have a pretty decent waiting list for work.