Yes, part 78 is there and the tension adjustment and tracking adjustment screws both work. The tension adjustment wasn't smooth though. There is no bearing or bushing to smooth out the sliding of the adjustment bracket.
The wheel adjusting bracket in the blade tensioning assembly looks homemade to me. It didn't move as though the spring was doing anything so I took it apart.
I just got this BN935 and I'm planning to do some restoration. Aside from needing new tires it functions perfectly as-is. The motor looks fantastic. The knobs look like they were originally painted a cream color. Was this how they shipped originally or were they bare metal?