When people say 1956 chev, I take it to mean Chevrolet "car" and not truck.
So it is a 56 car rear axle in a 50 truck. Cool!

If you are particular and appearance matters:
Measure the distance from the plate to the cable holder on the frame.
Take pictures and make a sketch of what you want.
Find a company that will make what you need, for example https://bruinbrakecables.com.

"Adding CFM to a truck will only help at engine speeds you don't want to use."
"I found there was nothing to gain beyond 400 CFM."