The rear sits pretty nicely! Looks like the bus never saw a full load of students in it's 23 years!
I'd swap the spindles for 4" dropped, put 2" blocks on the rear axle, and a nice set of 235/85R16 all terrains.
A 40 series Flowmaster I think makes the 6.5 sound a little "tougher" (it's such a rattler)
I wouldn't try to pull any extra power out of that motor. It really only needs to breathe a little better and stay COOL and it'll go a long way. Looks like it has AC, so it should have the clutch fan that engages more frequently than not. I see a lot of 6.5 busses that have what amounts to a constant-engagement fan and then a snap-on grille cover for winter.
Even I'm getting excited thinking about what you can do with that bus!
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