Brake Question

Drums or discs won't add very much AT ALL to the width WITH THE AXLES INSTALLED.

A drum is maybe 1/8" thick metal on the outside of the axle/ wheel mounting face, so drums only "add" maybe 1/4" to width.

Disk brakes might be a bit thicker, say, 1/4"--3/8" thick each, so they would add as much as 1/2"--3/4" and that might be generous.

"All the rest" of the drum/ disk "stuff" is INBOARD of the axle/ wheel mounting flange