[41LjH]

It is unlikely you have a 41 cab with a later seat because it's a lot of trouble to install the adjusting board and top cushion hinges inside the cab.
Post #5 is the correct seat for a 41 cab.
Attached are pictures of my seat. The slots below the window were mangled so I cut the top tabs off the seat. This may have been done with your cab.
The board at the base of the bottom cushion has three holes, 2 are visible top left of the second picture. To adjust the seat pull the base toward the dash and engage one of the holes over the peg on the metal riser( photo 3).
I don't have pictures of the later configuration.
If your seat is hinged at the bottom it is a 40-41 seat, see photo 1 and post #5.
If there is no evidence of a hinge between the bottom cushion and the seat back it is a later seat. Someone may have put a later seat in an early cab, but if the cab was made for the later seat you will find hinges attached on the cab below the rear window to hinge the seat back at the top, and another set of hinges part way down the back of the cab for the adjusting board. It these hinges are present look for evidence the gas filler was on the B pillar. If you see that you have a later cab because the gas tank was moved under the seat after 41. This can be confusing, I hope this helps.