Well, there were long gaskets between the fender and the inner fender and the body and inner fender (splash gaskets) and there were shorter gaskets where the inner fender mounted onto the firewall, but nothing between the fender and the cab. And on the back fenders, there were gaskets between the running board and the fender that looked sort of like an S. Some people in the 50s and 60s added fender welting, but you're on your own with that scheme. It isn't anything I'd do, because I've seen too many trucks suffer rust because those things invariably harbor moisture. If you've painted the cab and fender correctly (that is to say you've painted the inner surfaces of where the fender will mount and the inner mounting surface of the fender itself), you ought to be just fine.
