The first thing you need to do is find out how bad it's stuck and why. Is the motor complete? are spark plugs in all the holes,carb there, etc? Has the hood been on to keep water out? If theres nothing obvious, you can put it in high gear and rock it a little to see if the motor turns. It may just be stuck enough that you can't turn it by hand. Of course some engines get bent rods because people pull them while in gear to break them loose. You can pull the plugs and squirt something in the holes, every one has their favorite miracle substance. Rocking it with the plugs out will also tell you a little more. If it gets to where it turns over, you should be able to start it.

'65 C-10, 65 L-60, 65 C-80, 72 C-60 & and a bunch of old Chevy cars.
Never time to do it right, always time to do it over.