Shank size,?New Taller truck

[LeeJ]

Previously I had an 18 y/o Dodge 2500 4X4 short bed pickup pulling an 85 dual axle 25' Airstream dry weight of 6800lbs and the top of the ball on the Equalizer hitch was 18" to have the trailer pull at level with the shank horizontal length is 12" and the drop(?) verticle length is 8 3/4~9" and the head is mounted in the last bottom two holes.

My new RAM 2500 4X4 short bed sits quite as bit higher:
the Coupler height is 24 3/4"( from the pavement to the inside top of the 2.5" receiver) the ball height still needs to be 18" with a Receiver height of 19" for the Airstream to pull level.
What 2" shank-have the receiver adapter- (or a 2.5" would fit as long as the vertical part does not exceed 2" in order to re-mount the head) should I purchase?

thank you,

[Mollysdad]

I always start with e-Trailer because they use a tape measure on shanks.
Not all manufacturers measure the same. One 12" shank might be 12" overall, while another is 12" from the pin hole to the mounting bolts.
"Drop" is not the vertical measurement, but the amount a ball can be moved vertically. "Lift" is the same shank with the vertical part pointed up.