Sounds like the best idea up dating under the hood and keeping the inside as it is would be the best route. I know the a/c system in the truck melted a fuse sometime in the late 70s and wasn't used since, nor the heater. But I was planning on doing a new fuse panel and some rewiring anyway. I will look into the blower box and see what shape its in. I have a factory a/c 1975 parts truck as well so I should be able to at least have all the parts even if they need fixing.