Great project to honor your father:
If motor is stuck, you might try filling cylinders with a 50/50 mixture of acetone and automatic transmission fluid. Let it soak a few days, the solution might allow the motor to free up.
Good luck with the project.
If it's not stuck, but has been sitting a while you might want to pull the plugs and place a small amount of motor oil in the cylinders, turn the motor over a few times to insure the rings are lubed (with plugs out).
The procedure you follow to revive the engine is critical, you do not want to ruin the motor by getting in to big of hurry trying to start the engine.
Am sure others on here are much better mechanics than me and can give more in-depth advice on starting a engine that has been silent for a long while.