Hi cngodfather, welcome to Outdoorking.

There is a short-form workshop manual for the GX160, which is available for free download here:
http://honda-engines-eu.com/en/images/996.pdf

Unfortunately Page 47, which gives the dimensions you need, has accidentally been duplicated from the GX120 and hence has incorrect dimensions. I do not know of a free download of the full workshop manual, so I will just give the dimensions you have requested, as stated in the full manual.

The service limit for bore diameter without reboring is 68.165 mm, or 2.684". The service limit for the skirt diameter of the piston is 67.845 mm, or 2.671". However you cannot use a minimum sized piston in a maximum sized bore, since the maximum skirt clearance permitted is only 0.005". The permitted skirt clearance for a new or rebored engine is in the range 0.0006" to 0.002".

The ring gaps for new rings in a new bore are specified as 0.008" to 0.014" for the top and second rings, and 0.006" to 0.014" for the oil rings.

If you have any further questions about these dimensions, or about the engine overhaul, please ask them. We will be glad to help.