You can buy K/B direct right here at [link=http://www.mecoa.com/parts.htm]Mecoa[/link].

The gold carb is on the edge of being too big with my experience running a 3.5 O/B SS, it doesn't have much of a vacuum to draw fuel. Everyone has fuel delivery problems with it if you dont place the tank high, use a hopper tank, and good pipe pressure.

The neck diameter is .437", and the bore diameter for the gold carb is .312". Use these numbers if your going to compare to other brands. The black one is .265".

Car and Truck carbs, if you're creative with routing your throttle cable, are all mostly slide barrel types and there's always tons of them on eBay that would work if you can get a seller to measure one up for you, or find factory specs at their webpages.

OPS carbs are decent if you can find one, so are SuperTigre. OS is always going to be expensive. [link=http://www3.towerhobbies.com/cgi-bin/WTI0095P?FVSEARCH=carburetor]Tower Hobbies[/link] has a listing just for carbs, check them out too for what you might like or can work for you.

Another option is use a Perry carb. They are solely in the buisness of carbs and fuel pumps and buy direct from them [link=http://www.perrypumps.com/]here[/link].

Those are the choices I've encountered. The bad thing about it is, K/B is standard measurement, and all others are metric neck sizes.