Re: useful load of a Bus
6 bikes and 6 people, you are WAY under max wt.
I have a 88 pass bus converted to a car hauler. the car actually goes up inside the bus. It sleeps 6(qeen size bed and 2 fold out couches). when done it will have a 100gal + fuel cap. generator, TV table chairs, 2 tool boxes, area for spare parts, fridge, hardwood floor, table some cabinet storage. plus food and all the stuff you need to keep occupied during a trip and down time at the track.
Heck I bet you could even take a leaf or 2 out of the springs and still be just fine.