glenns towing,
I did a bit of part# researching using
GMpartswiki and results indicate only 1 part number for the oil pan being used for the GMC 305e (and 305a/305d) (see screenshots below). There are different part#s for the pans needed for 305b/305c/351/401/478 and a 3rd number for the 702.
The parts book also notes the dipstick (Oil Level Indicator) part is the same for all 305/351/401/478 engines with the exception of on Model N5000 series trucks. Thinking that indicates there is not a "deep sump" pan or dipstick for your particular engine and 1 Ton truck model.
The only odd thing that may negate some of this would be that your truck being a "fire truck water carrier" could indicate some changes/modifications may have been done for that special vehicle application.
Perhaps some of our resident "GMC" experts can chime in with more info???
Anyone with a GMC "305e" that can take some pictures with measurements of their existing dipsticks and oil pans to help figure this out???
Hope this may be of some help.
Dan
