Guess again! With the engine not running, key on or off, reverse is the park position on a Dual Range Hydra-Matic. It sounds like the parking pawl has gotten stuck in the output shaft, and won't release. If you can get the engine running and select reverse, the hydraulic pressure should release the parking pawl. If not, you'll need to find someone who is familiar with that transmission to drop the pan and free up the parking system. When the engine is running, line pressure keeps the parking system from engaging when Reverse is selected.
Jerry
