I have two KBV82s and one BVM91 and they are bolt in replacements, definately. I have tried it. Not sure on the 72 but I'd be suprised if it was any different externally. I am guessing the only way to tell them apart is to measure the bore/stroke.

I have a Viper that has the small tanks and a KBV82. I am thinking of putting the 91 in it. If I find I have too little fuel I will replace the header tank with a much larger one. There is heaps of room in the canopy (just a little hard to get things in there).