One might talk to the people at Memphis Equipment Company (http://www.memphisequipment.com/); they sell and service these things and sell parts for them. They are an excellent source for GMC 302 parts, and i have found them quite helpful. They should be experts on this problem. Note that they have a branch in Chambersburg, Pennsylvania, as well as the main shop in Memphis.
God's Peace to you.
d
