I haven't seen my pace mowers for a couple of years now so can't help with the engine number code ,hope to get a few out of storage one day.
Yes the Piston needs to be in the correct orientation to the barrel so the ring gaps are not in a port.
Victa / Pace put the carby and exhaust on the wrong side around 1960 ,other than the Pace a quick mention of other Victa backward motors would be the Sheerline , Viceroy and Cadet.
It's like Victa looked at Pope mowers and said lets copy Pope mowers (early Pope mowers are wrong) but Pope in the early sixties changed to having the carby on the same side as the earlier Victa mowers and Victa decided to follow suit.
The major thrust side of the piston should not be on the exhaust port side ,I did a quick test of temps today ,I quickly started a 2 stroke and measured 16 degrees on intake port side and 68 degrees on exhaust port side (motor not warmed up) so clearly it can't be good for piston skirt wear on the hotter side of the barrel.
In a car engine the surface temperatures of "Cylinder Head" and "Piston" can reach 260 degrees Celsius ,I would say the warmed up 2 stroke mower would get hotter than 260 on the exhaust side and some 2 stroke exhausts can get to 620 degrees ,obviously not a great idea to run the major thrust side of the piston on the hot side of the barrel.
