OK, I've done a couple of these for guys and left out that hokey brass spacer. Seems like the pieces were already dowel drilled at that time. If not a groove can be cut in the bottom of the brrl. channel on both sides and a dowel or rod glued in for strength. Just used an epoxy glue with some brown tint (artists oil paints work) added in miniscule amounts.
If you are handy with wood you can add onto the rear of the stock for more pull length, but it will NEVER match up with that wood, or look good.