On a 53 truck, the front fender is not connected to the running board (give me H folks, if I am wrong). The rear of the running board is attached to the rear fender.
Yes, you should be able to remove a front fender without removing the inner fender. You will have to loosen the radiator frame, in order to slip the fender out from from under the "arms" on the top of the radiator frame.
It is much easier and safer to remove (and install) the inner and outer fenders together.
Tim
