Aftermarket. GM did offer triples on a 235, but only on the '53-'55 (early) Corvette. Lots of us on here are running a similar setup, here's mine.http://rides.webshots.com/photo/2791114620092261295pSVaee
Now that I've seen a pic, I'm inclined to agree about a posible float/carb overhaul problem. I also notice the hose coming off the port on the manifold plugged with a screw(?). That could be a potential vacuum leak. Nothing major. Just needs a little TLC.
