Not all 91's and 92's come with a D35.
My dad has a '92 that has a D28. It is a supercab truck that has a 2.9, A4LD and a 7.5. Pretty much ALL of the undesirable drivetrain options... and power windows, power locks, etc... and it's red, on red, on red, on red. I hate that truck but it has refused to die so far.
Just as another fun example... you would think that truck being heavier would have got a D35... but I also had a 1991 single cab, short box, 4x4 with a 4 cylinder, with power steering and NO other options, that had a D35 in the front. And 4.10 gears!!!