Do the inner fenders on AD trucks interchange between 1/2 ton and 2 ton trucks? I know the Task Force series of trucks use the same inner fenders between the different models, but wasn't sure about the earlier trucks.

No

1/2 and 3/4 and 1 ton are same.

1.5 and 2 ton are same.

Thanks Grigg. Are they interchangeable between all years of the AD series trucks, or are the '54-'55.1s different from the '47-'53s? And to further confuse myself, do the Chevy and GMC trucks interchange?

Front fenders functionally interchange between Chevy and GMC plus or minus a parking light hole.

Inner fenders I’m not sure.. a brief look in the parts catalog and I couldn’t find the right section..
someone else will have to look and answer.

I think I found you the group and part numbers for the inner fenders, I am still not 100% certain if this part is shared with GMC, I suspect is would be.

Group 8.153 Skirt, front fender
47 COMM. left, front 3683075
47-53 COMM. right, front 3683076
48-53 COMM. left, front 3687381
47-53 UTILITY (exc. COE) left, front 3683081
47-53 UTILITY (exc. COE, SBC) right, front 3683082

54-55 COMM. (1stSer.)(exc. D-D) left, front 3700513
54-55 COMM. (1stSer.)(exc. D-D) right, front 3700514
54-55 UTILITY (1stSer.)(exc.COE) left, front 3700503
54-55 UTILITY (1stSer.)(exc.COE, SBC) left, front 3700504

For some reason the 47 driver side 3683075 is special, but eventually 3687381 replaces it in the parts catalog.
Sources:
Master Parts Catalog 30 June 1952
Parts and Accessories Catalog P&A 30 March 1957
-s

Those must be the Chevy numbers.
The GMC numbers from my 1939-1952 light duty parts book 1/2 ton to 350 or 370 series.

Group 10.0290 Skirt - Front Fender

...Nevermind, I can't make sense of it and don't want to transcribe the whole section... see attached picture of the book.

next time i'm under the hood of my GMC i'm gonna try to see why/where the GMC is different, tho it may not be obvious upon inspection.
-s