You might want to give Graves a call - (770) 461-7953 to see what they have. When I was there a couple of weeks ago to pick up a C4 for my 73, they were setting up a crusher to make some room - would hate to see your doner go to the jaws of death. I know they heve some 73-79s with power disk brakes (and I think that is a bolt on for your '70). I don't know about air for 67-72 series truck, but they do have a few of the trucks. I did the factory air add-on for my 73 (used a '78 doner truck). Not too bad a job.