Kmart your 7/8" shaft might have been replaced by a PO. All 2 GM20 and 3GM30 installed by Hunter in that era were using 1" shafts. As is mine also. And the one time I mistakenly grabbed 7/8" zincs at the chandler, they did not fit properly as there was a gap between the two halves.Errr. When I buy shaft zinks they are 7/8". And they fit perfectly.