Hien, I do not regard the GX160 as being a particularly good engine, or a particularly suitable one. It is as big as the Briggs 750, and was the "stretched" version of the GX120 family, resulting in a bit less efficiency and and perhaps somewhat less pleasing operation. That does not make it a bad engine, but one that is probably not much more suitable than the Briggs 750. The GX120 is the right size for the job, and was probably the nicest member of that engine family. I believe some other Outdoorking members have fitted GX120s to SB45 mowers, and seem pleased with them. I use a GXV120 (the vertical version, on a Honda rotary mower) for my regular home lawnmowing, and regard it as excellent.
The Briggs 91202 is a decent engine, in its time one of the very best. You should be able to have some fun with it, and learn a lot without much concern about making an occasional mistake.
