If you are really stuck, based on the photos of the motors I included with that article, some of which are taken on a mat board that has an inch ruler along the bottom, the Bachmann length from the end of one motor shaft to the other, looks like 1.125" (28.5mm). The motor length is about 16mm, hence I used a Mashima 1015 (15mm) to replace it.
The flywheels are pushed nearly all the way onto the new Mashima, all the way down to the motor body, with just a bit of space to avoid rubbing on the motor body.
I'm sorry, but I don't have a 2-6-6-2 or the original motor to measure.