I recently installed a Vintage Air in a '73 Challenger recently (have not started the car yet.) This is a factory, non-AC, 340 small block car. The engineering and installation of the system, I rate as a 7 out of 10. I feel that the design of the plate used to cover the blower motor was somewhat marginal and could have been designed better. Had I know before hand, I would have welded up the blower motor hole and then cut new holes for a cleaner look. I ended up painting the supplied cover such as one of the other posters mentioned. Also, I deviated from drilling into the firewall to support the Vintage Air box and fabbed a bracket to provide this support.
My current issue involves clearance between the thermostat housing and the compressor. I'm using an Edelbrock Air Gap manifold with the supplied compressor bracket. This installs the compressor directly above the waterpump slightly offset towards the passenger side. Using this heavy duty bracket with the Air Gap manifold results in the thermostat housing to nearly contact the compressor. The clearance is so minimal, I cannot install the upper radiator hose without making contact with the compressor. Perhaps this is not a problem when using a low factory iron, manifold. I suspect most aftermarket manifolds will result in this problem as well. IMO a slight redesigned for those who are using a non-factory manifold would solve this problem.
It sounds like you are using a big block and this last issue may not apply. Perhaps others have encountered the same problems and I would be interested to hear what they did to solve this issue. I have various photos of the clearance issues if anyone is interested.