This old photo from the South Dakota Department of Agriculture shows a CJ-2A with a 100 gallon tank mounted in the rear at or near Custer State Park. It appears there may be another tank across the cowl. Unfortunately, the photo isn’t very large.
http://sdda.sd.gov/wildland-fire/suppression/field-offices/mount-coolidge-fire-lookout-tower/
Might be a tool box across the cowl.