The manual is a misprint, ALL Dolomite autoboxes are 65s, I think there are internal differences between the models but only the Sprint came with an oil cooler as standard, the lower spec cars had a short U pipe between the 2 cooler pipe takeoffs.
You're definitely right about all Dolomites being 65's, I'd be surprised if a 35 could be made to fit inside the tunnel. Dolomites were the first 65 box I came across years back, they must have been one of the first cars fitted with them.
I think you're right about the cooler as well, I can't think of any other differences, (apart from production mods that they all got), AFAIR they all have the maximum number of clutch plates. Only modification that can be done is build the box up inside a Jag or Rover casing (or BMW if you can find one) and then you get larger servos for SECOND and REVERSE.
Just had a quick look and some 65 boxes do have smaller clutch packs so maybe the ordinary Dollies have those and the Sprint gets the full monty, but the clutch packs are easily uprated.