A/C in a 68

the 74 has different firewall holes, dash controls, etc. It can be done. Strip everything you can from the 74, ie... the entire dash frame as a unit, the entire a/c system. you may even want to cut out the firewall from the wiper motor to the passenger inner fender to get all the correct holes. Even if you went with the 68-9 a/c set up, you would have to make holes for the hoses, so, it is not that much more involved.