the GM “Baby Fishbowl” thirty-footer had an optional 351 gas V6. Only 10 % got the gas engine, the other 90% were obviously diesel. The '75 Flxible “Shorty” New Look 31 footer were often bought by transit agencies that needed a small bus with more power for routes with steep hills

Baby Fishbowl above, Flxible below

https://www.curbsideclassic.com/bus-stop-classic/draft-some-of-the-many-old-buses-of-the-seashore-trolley-museum/