From the Fall 2007, Vol. 40, No. 8, issue of the Keystone, page 31, which contains the caption for the centerspread photo of GP 30 No. 2224:
"....The only major change in the fleet came in 1967 when radios replaced trainphones. The antennas were removed but some retained mounting brackets...."
So, Ed, you're modeling one on which the mounting brackets were not retained, right?