Re: how different are short and long bus chassis
If it's the same "size" long bus and short bus (width wise), then look at the frame width spacing, most medium duty frames are same width or close and since they are C-channel they just extend the length between suspension points and walla it's longer.
Now notice most bus bodies sit on the frame rails and have clamps that attach them, so if the frames are same width then sure why not.
sit body on and clamp it down,
Now if your short bus is not an 8 foot wide one it won't work as easy since I notice you said P30 that is a 1ton Chevy Van?
so that frame wont be any where as beefy as a full size book mobile
So I dont know if this answered your question, grab a tape measure and scribble some paper
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