Digital backs for a 4x5 is a real challenge. I doubt anyone makes a sensor that big, and if they did it would cost a large fortune. That just leaves the "scanning back" and those are great for static objects, but you can't shoot portraits or anything in a short exposure.
The aerial photography company I worked for paid $490,000 for the Wild (Leica) RC-30. It had a lens that was 150 pounds. It used 9 inch wide rolls of film, 500 feet long. A single exposure was 10 bucks with processing, at the raw cost. It was mounted in a $20,000 gyroscopic mount. Bolted to a Cessna 206 with a 20 inch hole in the floor. The mount would keep the camera lens pointed straight down as the airplane buffeted, or had to tilt the wings or nose up or down while in the air. The exposure was 1/1000th of a second, and the film actually moved inside the camera during the exposure, to compensate for the forward motion of the airplane. The camera we bought was the 3rd to the last aerial film camera Leica made. It was the final peak and end of the road for film based aerial camera.
Now they are mostly door stops or display pieces.
This is the camera body and magazines in one box, and the lens is in the other box. The most expensive load I ever hauled in my El Camino.
This the lens with the lifting handle-cover on it. To drop it into place into the airplane it was best to have two men lower it down, or one really tough man.
This is the rear element. The metal square is 9x9 inches.