Difficult to say... Looks more like Montana to me - but different PC monitors show differently etc...
The bus has small-5 wheels and half-moon vents which would indicate a '71 model - but then it also has flat rear arches and paint upto the roofline (as pre-71) :?:
If it's original colour (or a re-paint of original colour), and the bus is a '69/70 (with late brakes bitted) I'd say Montana. Otherwise it's anyone's guess :|