If you really suspect a seized motor, then remove the bulhead covers and put a socket on the crank and see if it will turn by hand.
I'd have to go with George's diagnosis on this one, it sounds awfully like the starter motor. If its just not been used in a long time it can be a sticking issue, you can sometimes free it up by rocking the car back and forth in gear. That should also allow you to feel if the motor is trying to turn at all too, quicker and easier than the first option of removing the bulkhead.
Julian
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