The carbs on your 78 are different, and the airbox and intake rubbers slightly changed as well. But no problem, just attach that new filter to your airbox, it will fit the same. It will flow more air than the stock pleated filter (but less than 4 pods) so it is likely you'll need to adjust for that somewhat. I've set up a similar filter arrangement, but will not have the bike running for a while yet so can not give you any advice on carb setting. Check back on previous discussions and you'll find some help.