I have a 1975 nova that had a lot of problems, with wipers and a/c controls. The wiper system is a mess, so I replaced it with a 1985/86 Camaro wiper motor. My steering column was just a shaft, so I replaced it with the camaro column w/tilt. that helped with the wipers, just hook it into the column system. Now the a.c control panel would not change the vacuum. I did some reserch and found that a 1976 control system would work ok, but the vac system was different. I had some help with finding the vac schmetatic for the 76, but did find what you need for the transfer. The #6 hole is the vacuum source. then you apply the source and locate the defroster, heat and hook up the vacuum hoses one by one until it it's done. You will have one vacuum hose to plug on the 75 because of the double pull diaphragm. It will work just leave your instrument cluster out till it all works . You also nee the vac manifold to the 76 nova.I found the control at - [email protected] -. By putting in a different steering column.and wiper motor assy I solved many problems that chevy caused . only in 1975.