I had the same problem.
I had a 3/4 inch gap at the top of the fender.
The running board seemed to take care of the bottom.
I tried to adjust the running board outer fastener by adding shims but didn’t help much.
It wasn’t until I put in the fender braces that connect the radiator shroud to the outside edge, inside of the front fender that the gap closed up.


Mike


1940 Chevy 1/2 Ton presently... Almost done
1940 Chevy Business Coupe... In pieces