Thanks for the images, Mark
We used that filler at the four corners of the large roof "panel".

The long front-to-rear connection "joints" should at least be carefully cleaned, sealed, and primed before painting.
This would pertain to all 47-55st panel-body A-D vehicles:
1/2 ton Panel and Canopy Express
1 ton Panel and Canopy Express
two styles of 1/2 ton Suburban Carryalls

Pickup trucks (all truck cabs) have similar "joints" between the top and bottom of the cab.

Tim
1954Advance-Design.com
1954 3106 Carryall Suburban
1954 3104 5-window pickup w/Hydra-Matic
The 216 and early 235 engines are not "splash oilers" -- this is a splash oiler.