Bonneyman,
I have a Thorsen 77J 3/8" drive open head ratchet for you; the overall length is 7-1/2" while the head width is 1-1/8". This design was not intended to be disassembled during normal use or a normal lifetime. It was instead designed to be easy to clean and lube and perform reliably under the worst of conditions. Here's some photos:
Overview with the gear cover removed and shown below the ratchet
Close-up side view of head. Note there is a cavity in the handle shank with spring and ball that keeps tension on the V-shaped lever/pawl assembly. The lever and pawls are all one piece. The pawls each have two teeth that engage the drive gear. The drive gear has 30 teeth.
Top view of head. Note the pivit pin for the lever/pawl assembly. This pin is pressed in.
I'm guessing the drive bit
could be pressed out from one side or the other, which would allow the gear to be removed/replaced, but I have never had reason to try this.
Hope this adds to the body of ratchet knowledge....