Your truck will be equipped with 1/4" pipe thread fittings which became obsolete in 1975 with FMVS121. 3/8 pipe thread has been the standard of the industry since 1975. I would replace all 4 air chambers. If you don't have spring brakes on the drive axle, I would add them. Heavy trucks had spring brakes by 1966, but I don't know about Chev. We use either Haldex or MGM spring brakes and chambers. There are some really bad unbranded ones out there. For hose we use Velvac, Sloan and Meritor air brake hoses. I buy quite a bit of stuff from these guys. Their descriptions are not very good, but you can go to the manufacturers web site.
https://www.finditparts.comI find places like NAPA prices outrageous. I operate a fleet for a profit. I'm not so sure I would turn a profit if I bought parts from local auto parts.
