Thanks Chuck....we got it. The top bolt turned out to be a female hex head, that may be the metric equivalent to a 3/8". Anyway, we found a 3/8" hex head socket (brake caliper tool) that we could get on a rachet, and barely make the clearance to loosen it with a box-end wrench over the end for additional leverage. Definately a two person job...one from top to guide and hold the socket in place, and one from bottom to loosen. Good thing these things last for 29 years!
Barry