Frank S ,
Can you send me a picture of the machine?

I think that the machine that you have would be a store brand one.
The pace brand to my memory started being made around the 1970's and if it was you would have a carbie on it that has a wind vane on top either in plastic or metal.
The muffler was what they called a torpedo type. If you go to the area Parts list and Repair manuals you should be able to pick out the carby on your mower. I will forward you the access code(private mail) so that you can have a look.