Welcome from Texas.
Let's get technical, the motor is most likely not "seized", that would be a mechanical failure.
It is prolly "stuck" from sitting, the rings tend to rust to the cylinder walls.
There is a good chance you can "unstuck" it. Pour a cocktail of 50/50 ATF/Acetone and pour a few oz into each cylinder and let it sit a few days.
Then put it in third gear and rock it free. Good luck.
Start a thread in the Project Shop area.