I did this last month. A little while with a Dremel and I was set. For finished slant back furniture, I'd check gunbroker. I happened to have a spare from another Vepr that I converted to pistol grip. As mentioned above, it was necessary to make the notch for the trigger guard deeper since I pulled it from a 5.45x39 vepr.
This is my 23" 54r Vepr with the adapted stock.