Here is a link to the molded ductwork that creates most of the problems with the Firebird A/C installation. It is the third diagram down, and within the most-excellent dash disassembly procedure provided by Hitman.
http://www.78ta.com/resto/rdash.phpThis ductwork is for a factory A/C car and includes the lap coolers, which I dont presently have but could get from an A/C car. The problem is how to tie into the ductwork at the end vents and the center dash vents. With the new kit, the heater/evaporator wont link to the molded pieces, so one has to tie into the last piece at each vent (end, center, and lapcooler) or to the vents themselves. This is where creative fabrication skills are needed. I could disassemble the dash and send the end pieces to Classic (or Vintage) but then use of the car is lost after sending parts off, the dash is in pieces, and who knows when the adapted parts will return.
The only advertised direct-fit kits I've seen are for the 67-69 firebird. For 70-78 firebirds Classic offers all the parts under the hood with a Sanden compressor, but nothing under the dash. The 70-78 camaro kit can be adapted, but the issue with molded hoses remains. Using the center vents from an A/C dash bezel is cleaner, but how to adapt to the large molded cover for the center vents remains.
This remains the hurdle for me. I hadn't heard about the ambient sensor, so that is new also. The reason the aftermaket kit is atttractive is that the stock kit dominates the engine compartment and the firewall wold have to be cut, etc.