I put this together in 2 small Garages. we were cramped.If I was going to build a Garage for a car restoration. I would make it at least 3 bays.A bay for the body ,a bay for the Frame and then a general work area. so at least 32 wide. then the depth should be at least 25 to 30 I would also go as high as possible so you can build a loft area for parts.
storage.I am sure you may know this buts in today's market its cheaper to purchase a car done then to build one.Not even counting the cost of a new Garage.
Good Luck I have seen lots of project started and never finished with a Giant outlay of money and no way out.
I away recommend right a budget then add to it and make sure your able to handle it
Drive train rebuild $8,500.00 Paint and body $8,500.00 to 12,500.00 Interior $4,500.00 Chrome and bright work $5,000.00 Wheels and tires $3000.00 Is this what you were expecting?
Good Luck and Enjoy