Where can I get one of the short LOP stocks that came on the Ranch rifle  #5820 ?

The Ruger model 5820 doesn't have a shorter synthetic stock. The LOP is 13" for both the Model 5817 and 5820.  The length difference between the two versions is in the barrel as the 5820 has a 16
?" barrel while the 5817 has an 18"
barrel.  





If you want a shorter stock, I have a birch stocked 583 Series Ranch Rifle and I cut 1" off of my buttstock plus added a Tech Sights rear sight (it moved the aperture back
½
") to reduce the 'Heel to Aperture' distance from 15
½
" down to 14"; the same as my M1 Garand, M1A, and M1 Carbine.  I think it looks just fine and now I don't have to stretch my neck to get a good sight picture.