Hello Shak. Welcome from a fellow Crossover Danbury owner!
Things that spring to mind:
'Early bay': Round bumpers, low front indicators, large VW emblem on front, Volkswagen script on rear hatch, sliding door (handle and mechanism etc), fuel filler flap (although moved further back to clear sliding door this year), instruments, indicator stalk, brake fluid resevoir above kick panel, cab door 'furniture' such as window winder, lock and release levers (chrome), dash heater controls (two red, two blue), grey wiper arms.
'Late bay': Fresh air vents in cab doors, front wheel arches, rear lights, rear vents, Type 4 engines and the modified engine bay and revised engine hatch. Pretty much as you would already know.
It's difficult to specify what was one year only, as some parts were carried over from the earlies and others continued into the lates, ie rear wheel arch profile slightly changed from the '71 model year, and the early style sliding door stayed until the '73 model year etc. I believe some parts to do with the braking system were specific to the crossovers. Others I know of are the front arches, whilst appearing the same as late ones, are slightly different, I assume to take the bumper with step. The rear bumper is crossover specific in that its mounting brackets are different.
I've just mentioned some of the more obvious things, most of which I have discovered myself, having been brought up with a Danbury crossover in the family, but having owned lates, and then recently having renewed my aquaintence with the Danbury crossover by buying the one I have now!
There are obviously loads of other detail diferences, some of which I'm sure others will add!
I hope you'll pop some pics up of your bus for us? 8)
Doug