Just measured mine with 9"drums i got 8 7/8" from back of spindle to frame, the wheels are on it i can pull them tomorrow and get a better measurement if ya need it.
no wonder I could not find it on my scale....I thought it was in MM
can you measure how thick to the face of the drum?.....where the wheel bolts on. I use Mustang II spindles...so the measurement to a factory spindle doesn't transfer.