make up a adapter plate, thats all i did, get some sheet metal, cut it to size to fit on your carb with the bolt holes in the right place then adapt that to fit onto the k&n.
thats all i did putting square top carb filter onto a round a round top one then did it again to swap back again. if you have the auto choke id ditch it though as they are crap and make up a manual choke conversion for it.