.....Old Cars Weekly also publishes a Buyers Guide. I've used it for many years. But, as said, its a guide and it all depends on condition. I think the book stores carry it. The guide comes out once a year.
According to my September 2020 issue of the price guide for 37040 3/4 ton is: # 6 condition is 1720 for pickup and Stake 1240.
( #1 is 43,000 pickup, 31,000 for Stake bed. (Note: there are VERY few #1 vehicles, period!!)
For what its worth most cars at cruise ins are #3's but the owners think they are #2's and #1's so beware!
....just to mention it list a #3 condition as 19350 for pickup and 13950 for Stake body.
The old cars report Price Guide comes out quarterly. Maybe this will give you some idea?!!