I did one of these by removing the bolt, a carriage bolt and square farmer's nut, in my case, and replacing that with a hardwood dowel that was epoxied in place. This was done after stripping the old finish and removing soaked in oil.
Then I evenly planed the stock cheeks off about 3/32" on each side. You could use a belt sander to do this, but both cheeks must be completely flat. Two pieces of black walnut veneer were then glued on using Titebond II wood glue, to completely cover the dowel repair. Clamp carefully to get a close fitting joint. I made my approx. 1/8" thick black walnut veneers by making a simple fixture to run them through my thickness planer. I've found that the Titebond II makes the most invisible glue joint so long as the joint is closely fitted. Then the new veneers on the cheeks were carefully sanded down to meet the action and stock. To further conceal the glue joint, you can make some artificial pores across the glue joint with the point of an X-Acto knife. Too few is better than too many here. The whole stock was refinished with a reddish dark Watco Danish Oil finish.
I was lucky in that the grain of the original wood in the bolted stock cheeks was relatively straight grain walnut. With a little time matching grain, a closely fitted glue joint, and the dark reddish walnut finish, you had to look hard to notice it had been repaired. For a field grade that isn't worth the cost or time of restocking, it was light-years better than the original Bubba repair.
A lot of Parkers have been repaired by dowels or screws or bolts through the stock cheeks, because the tangs are tapered like a wedge. While you have the stock removed, it is a good idea to do the "staple" repair in the head of the stock to prevent future problems. You can Google "Parker shotgun staple repair" to see what I mean.
