Think you'll be glad you did that. I used to own a Harley Night Rod. Worst suspension for a bike I've ever owned. Had Penske build me a set of double adjustable coil overs for the rear and they replaced the cartridges in the forks with an AK-20 Axxion Cartridge Kit from Traxxion Dynamics.
http://www.traxxion.com/harleydavidsonforkrelated.aspx
Whole package was around $2500.00. That was around 2010.