My 1986 GE "dual wave" range (shown above) finally gave up. The attached microwave broke and wasn't able to be repaired so the whole giant thing became useless. I replaced it with a GE Cafe electric range ( I prefer gas but it isn't available in this neighborhood) and Whirlpool over the range microwave. They have been in use now for a couple of months and I am happy with both.
Had to add a board to hold up the top of the microwave. It attached using screws through the cupboards on either side.
The board and the metal hanging bracket that comes with the microwave.
The manufacturer photo of the microwave below. The Whirlpool decal is a sticker that I carefully removed using a hairdryer to heat and soften the glue and then worked dental floss behind it until it came off.