None of the AD or TF trucks came from the factory with a heater installed. It was a dealer installed option. The "approved" heater option was made in GM's Harrison Division, which made all of the radiators as well as heater cores.
None of the five AD and TF trucks that I have owned had a "factory" heater. My old 51 had a Nash heater, my current 54 has a Mopar heater and three TF trucks had Arvin units. The Harrison heaters were pricey so many owners opted for a $2 junkyard heater. My dad claimed he got the Mopar for the 54 3100 by rolling dice right on the shop floor.

Sooo... any period correct heater is considered correct for an AD or TF truck.
Same with bypass oil filters. Dealer installed option. I've seen Fram and Franz on them as well as the AC. Any are correct.

~~ Jethro
1954 3100
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1951 3100 (gone) / 1956 4400 (still in the neighborhood) / 1957 6400 with dump body (retired) / 1959 3100 panel (in the woods junked) / 1978 Custom Deluxe K10 / 1993 S-10 4.3 / 2004 Chevy Crew Cab / 1945 John Deere H / 1952 John Deere B / 1966 John Deere 2510 / 1967 John Deere 1020