I had the same problem when I lived in Fairbanks, Alaska. All of the non paved roads had glacial sill which is you described when dry is "like talcum powder". From 1969 thru 1976
I had a 1969 4x4 W200 power wagon, 318 ci, and the old style air filter on top of the cab. Back then the pan was filled with oil below the air filter. It was the most efficient design for
trapping dust of all sizes, but a little messy when cleaning and putting in new oil . My Gen 3 dodge air filter works Okay here in the lower 48 but not as good as the 1969 power wagon.
I am convinced the the Gen 3 stock air filter box design is flawed. 100% of all Gen 3 trucks that I have looked at have some degree of box-to fender separation. As an engineer I know that the design
engineers at Dodge designed the box to remain "tight up" to the fender - with no separation. One can purchase 3M weather strip with an adhesive back in different sizes to replace
the OEM foam that attaches to the metal fender. But my problem is the stock air filter box no longer fits tight up to the fender air inlet to the box. The front bracket (attached with
a 10 mm hex screw) of the box has twisted and is no longer true. And the female grommet which is part of the battery tray assembly (that receives the nub on the bottom of the box)
has been pushed down maybe 1/2" or more.
I would say at this time that a new stock battery tray assembly and air filter box is going to be the likely stock fix.
I had a 1969 4x4 W200 power wagon, 318 ci, and the old style air filter on top of the cab. Back then the pan was filled with oil below the air filter. It was the most efficient design for
trapping dust of all sizes, but a little messy when cleaning and putting in new oil . My Gen 3 dodge air filter works Okay here in the lower 48 but not as good as the 1969 power wagon.
I am convinced the the Gen 3 stock air filter box design is flawed. 100% of all Gen 3 trucks that I have looked at have some degree of box-to fender separation. As an engineer I know that the design
engineers at Dodge designed the box to remain "tight up" to the fender - with no separation. One can purchase 3M weather strip with an adhesive back in different sizes to replace
the OEM foam that attaches to the metal fender. But my problem is the stock air filter box no longer fits tight up to the fender air inlet to the box. The front bracket (attached with
a 10 mm hex screw) of the box has twisted and is no longer true. And the female grommet which is part of the battery tray assembly (that receives the nub on the bottom of the box)
has been pushed down maybe 1/2" or more.
I would say at this time that a new stock battery tray assembly and air filter box is going to be the likely stock fix.