Mufflers

After going over every inch of the electrics, my KZ started right up. Trouble is, its loud, like Harley LOUD. Which makes sense when I look and there's no baffle in the muffler at all - you can see straight up the exhaust to the bend in the header pipe.

What's on it now is some sort of aftermarket 2-1 setup. I see MAC has one for '78 & up KZ400s, but not for the '77s. Are they close enough to be made to work ?

Or should I just get a generic slip on and be done with it ? Is there a brand people like ? Quieter is probably better - my late-night commute takes me right past the local cop hangout down the block