I recently acquired a 135 evinrude from a friend that has a crack in the lower unit. I am having trouble finding what lower units are compatible with it. The motor has been painted and the ID plate is missing. The motor appears to be a late 70's motor. Is there another way I can be sure which lower units work on this motor? Besides comparing them side by side. I have found a 76 model three hours away, but would really like to have a better feel for the compatibility before making a dry run. Any advice is appreciated.