I just went through this same door latch problem on my ’53. If the door is still ¼ inch open, it is not fully latched. One would logically think, the striker plate needs to be moved inward in the jamb to tighten the gap, however I found the opposite to be the remedy. By moving the latch horizontally outward toward the door as far as it would go, it permitted the door mechanism to fully engage and the door fastened properly with no gap.
The striker plates for the 47-51 trucks are slightly different than 52 and later but the principle is the same. Looking at pictures online, it appears 47-51 trucks may only have horizontal adjustment (horizontal slots in the doorjambs), whereas 52 and later have slots for vertical adjustment (Striker Plates) as well as horizontal slots in the doorjamb?
First, try the horizontal adjustment as I did. Also If you have any vertical adjustment, try moving it down a bit. Over time, doors tend to move down not up. If all else fails, a small round file can give you another ¼ inch of adjustment to the striker plates.
Like many, we had my doors closing and fitting near perfection at the paint shop until we installed the new weatherstrip.
http://i1291.photobucket.com/albums/b542/RdLessTaken/IMG_85261_zps90bf2b98.jpg
