GXV120 What? (A1, A12, A14, A1L...) Trying to purchase parts

I need parts for an older (1988 or so) lawn mower engine. On Jacks they list about 15 different GXV120's S/N ranges that my S/N falls in but after the GXV120 is a designation my engine does not have. The mower is a HR194 PXA and the engine is stamped GXV120-1771628 so how do I tell if it is an A1, A1#, A12, A14, A1L, A1L2, A1LA, D1, D1#, D12 blah, blah, blah?

I am replacing the rings. It has been a while since my last top end but back then you could purchase top end, carb... gasket sets much cheaper than individually, is this not the case with Honda mower parts?

Thanks, Kevin