will a rear wheel off a dyna fit on a sportster if so do the sportster spacers fit

 

Don't think you'll fit a 4.5" wide rim on the back without modifications, it's quite a bit wider than the standard wheel. Highly unlikely that the belt would clear the tyre. Sportster spacers would definitely not fit.

 

Passed close to your home town only last week!

Tell us what year your Sporty is and tell us more about the Dyna wheel. I've swapped wheels around between models, but it isn't an exact science, as nobody has yet written the definitive book on what fits what.