yes there's a secret, but nobody will tell
this is the 56? the TF doors are a PITA - if too close to the fender, the fender might be back a bit further than necessary - then if it's too low on the latch side, it will be too close to the fender at the bottom, which might be that the bottom hinge [inside the door] needs adjusting out and the top one in [also inside door] - the pillar side of the hinge mostly flushes up the face, but can have some influence too
confused? one way to shove things around is to loosen both hinges in the door slightly and close it while holding up on the handle, once it's shut and fitting passable, climb inside and tighten the hinge bolts - once you get it close that way, the striker parts can be adjusted to fine tune closing
the ideal is to have about 3/16 - 1/4" gap all around, but the dog leg doors were a problem even at the factory, and it's not unusual to see a truck where the doors seem a slightly different shape than the opening, ya just have to keep futzing until it works ... assuming the hinge pockets on the cab are in good shape
Bill