Very few moho's are built on chassis made by the OEM. The vast majority are built on OEM vendor supplied chassis. The major players in the market over the last 20-years have been Freightliner, Spartan, Workhorse, IHC, Gillig, National, Oshkosh, and a few other lesser known OEM's.
The OEM of the vendor supplied chassis can make a big difference when it comes to getting any parts or service support down the road. Gillig prefers to not acknowledge they have ever built a moho chassis just like it is as if they never built a school bus back in the day.
Most of the parts and pieces are stock off the shelf medium and heavy duty truck parts. But there are some parts and pieces that can be a real bugger to source if the chassis is not supported by the OEM.
Before I pluncked down those sort of $$$ for a moho I think I would need to know who made the chassis and how hard it is going to be to find parts and service for it when the need arises.