Hi Ty.I'm not sure if I can help you with the engines number that you are looking for however I do know some of the sequences for the earlier models.They are as follows.These are for the victa's
Model 1 1 to 10,000 With no 125 on the front crank case.However there is some debate that it only goes to 8,000 Now.The first 400 had letter with them,these engines where made to run pumps not mowers.
Model 2 10,000 to 100,000
Model 2A 100,000 to 110,000
Model 4 Automatic 110,00 to 130,000.These were all straight numbers no letters where in there. I have also found that the Model 3 numbers were usually over 140,000,but don't know to what range.After that the number system was thrown out the window. I hope this helps in your research.
