How to unlock a frozen engine
 

Step 1. Remove all spark plugs

Step 2. Fill the cylinders with Diesel fuel put plugs back in

Step 3. Let it sit for about 2 weeks.

Step 4. Take out the plugs, using the crank pulley nut attempt to manually turn the engine over. If it dosnt move put the sparkplugs back in a try leaving it be for another week.

Step 5. When you do get it moving freely turn it over by hand until you have most of the diesel out of the cylinders.

Step 6. Install new spark plugs, change all the fluids and a new strong battery. Add a little fuel in the carb and see if it starts on its own.

If the engine started then you are fine, but if it didnt start or even try then there is something else wrong with the engine.

If the engine is running, you will notice it's may not be running real smooth, and is blowing a some blue smoke out the exhaust. This is normal, unless it keeps smoking after all the diesel has been burned out of the engine.

This older gentleman at a local hardware store told me 1 time he had a chevy 283 sitting around. It was locked up. He took the plugs out and sprayed wasp and hornet killer into each plug hole and put the plugs back in.
Went back to it a couple weeks later and was able to turn the engine over with a breaker bar.