Progressive 412 Shocks TECH:

If you want to lower your Ironhead (or K-Model) using 13 1/2" shocks . . . 

 The best way to mount them is to tighten up the top where you want them, and leave the bottom loose and see where it wants to locate on the lower shock stud.  Then make spacers and shim it, so you don't pull your shocks one way or the other.  No Binding.  I had to design a spacer the correct width to be just about in-line with the step, and then I use a heavy washer.  These shock ends were a bit narrower than the stock -52 OEM shocks I still had on the bike.

The first problem I noticed after I tried setting the spring tension was . . . These 75/120 Rated Springs are way, way, way too soft.  On the stiffest setting, I could bottom the fender on the tire with my hands.  Shit.
This sucks.  Of coarse, Progressive tech support will tell you "these really aren't the correct application" but, running 13 1/2" shocks on your ironhead is one of the most common things to do to these bikes since the early 60's . . .  Back then they just used panhead shocks.   I think they just send these so you have to buy another set of springs (so search for a great deal on your 412s, preferably with 120/170 springs).

 Too Weak (above)

This is what you want (or stiffer) 120/170

One thing that's kinda cool . . . you can shit-can the ugly, top spring covers since the springs have a beehive
type wind at the top to hold the spring retainer.  I think they look best with all that spring showing.

 Now I want to lower the front about 3/4-1" by maybe cutting down the springs, shortening the tubes, or maybe the Progressive Forks Springs . . .

Get this thing down . . . a bit 'n da weeds

Low for Go Bro