There is no difference between the M&S and the Wayne 80 gas pump. After Wayne merged with M&S Wayne moved their home offices and manufacturing plant to Salsbury, Maryland.
Not may people know this, but before Wayne purchased M&S, they published a large brochure showing their next pump, the Wayne 80, I have a picture of it. But...they purchased M&S, and M&S already had a 80, so Wayne never made any of their 80.
After, Wayne purchased M&S, they continued to make the 80, they just added their name to the ID tag. The first parts manual that Wayne supplied for the 80 is an exact copy of the M&S manual, just a name change. After Wayne made the 80 for a year or two, they reduced the number of 80's versions from around 32 to about 20, but everything about the pump stayed the change, so, everything about the M&S 80 and the Wayne 80 are interchangeable. So...if you don't want a M&S 80, just find some Wayne 80 faces and a ID tag, you will have a Wayne 80.