Installed Progressive monotubes on my 2004 FLHTPI. Was super easy to install them.
A few things you must have to install them,
1. A 1 and 3/8 inch closed end wrench, I got mine at NAPA auto parts
2. A 16oz bottle of your choice fork oil, I used the Screamin Eagle oil from the stealer
3. 2 new fork seals and I got 2 new lower fork screws and crush washers at the stealer
4. A HD fork seal installer or make your own from a 2ft section of 1.5 inch pvc pipe, cut a slice all the way down one side of the pipe and scribe the other side side so that you get a hinging effect so it will slide easily around the outer fork tube, put the lower fork on a 2x4 piece of wood and use a small block on top to drive the pvc pipe down and seat the seal
5. The lower fork screws i had to use a 3/8 impact gun to remove them, and use it to install them, It says to torque them but the fork assembly will just spin if you try that, I used blue locktite on mine but it does say red, my choice up to you ( air impact gun )
be careful not to go to tight on the reinstall
If you follow the supplied instructions it goes quite easy !
Just go slow and do one fork at a time.
If you are doing an electra or street glide each side is different so make sure you pay attention to the instructions, Road king I believe is the same on both sides
Good luck and cant wait to ride mine !