If my memory serves me correctly I believe the stock "L" pulley is 2.93 not 2.80. Harley pulley stock is 3.25 so if this helps you then my typing was worth it.

I have a factory 2.93 pulley I was planing on swapping out but it think swaping the lower pulley for a 4# or 6# would be a better choice. If you leave the bigger pulley on the blower you will have more belt contact and hopefully less chance for belt slip.

I plan on swapping out my lower for a 4# upgrade which should yield 12# of boost.

Also remember that if you change the intake parts to flow better you will pick up 1-2#'s of boost as well.

If you put too much boost into these M112 Eatons blowers i hear they will pump out way too much heat and therefore the air charge temperature will suck the life out of the increased boost.

Most people say 13-14#'s of boost is about the max you want for this motor anyways.

Hope this helps.