I would not worry about the tires to much. Flat spots were a lot more common in older tires.
If your concerned push the car forward and backwards once every other week.

Is the car numbers matching? If yes, I would fix your motor. If no, I would try to find a running motor and just drop it in to keep the car on the road.
Then work on a rebuild of your present motor.
Pulling the motor is not as complicated as it looks or sounds. But, I would pull the motor and transmission at the same time.
I just swapped out my turbo 400 and it was much more difficult doing it by its self.

Any members live by you that could give you a hand for a Saturday?