Re: Engine and Transmission Questions - looking at two busse
As far as rust, with the exception of the bus I parked in the ocean, rust has not been much of an issue with the other michigan buses I've owned.
Some blue bird buses are galvanized which is an option of you are concerned with corrosion.
There is a link in skoolie that helps you identify an at545 vs an mt643. It would be a great idea to have the photos of each trans handy so you can identify the trans on any particular bus when crawling underneath.
Also, the rear end ratio is occasionally printed on the vehicle info tag near the driver seat, and almost certianly printed in a metal tag attached to the differential cover.
Lock up torque converter, inline engine, and 4.44 or 4.10 rear end ratio is super important for fuel economy.
If you were burning diesel fuel, the wrong powertrain that gets 2mpg less than the alternative would cost an extra $500 on one trip from Michigan to California and back.
Quis custodiet ipsos custodes (who will watch the watchmen?)