1949 GMC 3600?? Chevrolet??

Either way, There is fender welt where the fender bolts to the cab. There is "anti-squeak" where the fenders bolt to the inner fenders.

If you do not have one, you might want to obtain a 47-55 Factory Assembly. It would be helpful for either a '49 GMC or Chevrolet (even though most diagrams are for 54/55-1st series Chevrolet).