Rodent proof old garage door with uneven driveway
There's a problem. Rodents can get through tiny gaps. Doors generally need gaps around them. 

Some ideas -

Remove whatever it is that is attracting rodents. Tidy up the floor. Put edible stuff into metal containers (I use metal bins with metal lids that I weigh down with heavy bricks).

Get a cat and fit a cat-flap. Cats love chasing rodents away.

Graft new wood on around the edges of the doors using glue, dowels, screws or whatever methods and hardware you have to hand. This means taking the doors off after scribing the required shape onto some the donor timber. If an enlarged door would scrape the ground when opening, you'd have to lower the ground or abandon this idea.

Have the door close against a fixed frame. You would probably need a rubber sealing strip or equivalent to close up gaps. Rodents chew through rubber.