This won't get you to the Oakland Roadster Show, but-----It works and its cheap. On all the rods which I build, I take great care to make sure that the hardlines for hydraulic brakes, fuel tank, and transmission cooling are mounted securely to the frame.
When I get to the wiring, I seperate it out into bundles depending on what corner of the car its running to, wrap the bundles with black electrical tape, and use nylon electricians tie-wraps spaced about 6" apart to tie the bundles to the hardlines.
The black tape makes the wiring virtually invisible, and it is well supported.