Figuring that Ed’s bus is drawn as a front-engine Blue Bird, I went to their website in the hopes of determining what engine(s) they use. I can verify all the front-engine Blue Birds use diesel engines, but could not determine whether they are already turbocharged (as is the case for most diesel truck engines). But in the real world I would expect at least a 50-50 chance that school bus diesels already have turbos, for efficiency and economy.
That’s what you get for buying your “turbo” from Bean’s End.