Here's a trick for taking those GCV160 carbs off and putting them back on. Honda mentions it in the shop manual for them, except they have a specific stud for it.
Get a couple of 6mm threaded studs that are about 4" long. Take one of the bolts that holds the carb and related things in place while holding on to it all, then screw in one of the studs. Take the other bolt out and screw in the other stud.
The studs will hold everything in place and help you line it all back up. When putting it all back on, reverse the process with the studs and bolts.
For the carb, (this is a different one, but the markings will be similar) Look for these two stampings.

Those numbers, and the serial number on the engine will point you in the right direction for getting the right carb.
Check with your dealer, or this place is a good online source for parts.
http://www.boats.net/parts/search/H...K2 TDAA LAWN MOWER, USA/CARBURETOR/parts.html