as far as a shorty that looks like a big bus.. all the major manufacturers masde (make) them..
one of my shorties is a carpenter on an international chassis.. carpenter becamse "crown by carpenter" in the mid 90s and ceased in around 2002.. i still see their busses show up..
bluebird and thomas put short bodies on freightliner, GMC, ford, and International chassis.. one of mine is a short 6 window on an international chassis.
Amtran / IC only used international chassis.
in older busses.. Wayne / Superior / Ward / Carpenter / Thomas / Bluebird all put their busses on the various chassis.. (ford, GMC, International, Freightliner)..
later on into the early and mid 00s only 3 big players remain (to this day).. conventional Hood-nose busses only come in a few flavors these days..
Thomas Safe-T-Liner C2 (real modern looking sloped windshields)- generally freightliner based (at least partial daimler owned)
IC bus - fully international owned and uses only international chassis.. looks most like its roots as a ward -> amtran -> IC bus,,
Bluebird - Vision - proprietary chassis - gen 1 reminded me of the family truckster..
in modern times neither CAT nor international make school bus diesel engines... in effect reliability issues related to emissions in the 2008+ years destroyed the reputation of CAT and international for making MD and some HD engines... so they mostly pulled out of the on-road market..
Most Bluebird visions and new IC CE busses come with cummins 6.7s, Thomas offers Mercedes engines as well as Cummins in theirs nowadays..
there are other outliers of busses (REAL crowns, gillig, lion, collins) that you occasionally find in the used market .. crowns and gilligs are collectible and go for BIG $$$