It should work. It may take a bit of fitting to get it just right but that is to be expected. Each gun is fitted with the stock when it is made and there can be small differences that can make a swap fit poorly. It might be a close or tight fit and need some material removed or it may fit loose and need some bedding done. You never know till you try it. My 1894fg stock will interchange with my new 39a but there is a small gap at the tang on one and a gap at the front on the other indicating a difference in the tang length.
Mines not a pistol grip its straight stock. I just fit a birch stock set from a 44 Mag 1894 onto my 39M. I also had and tried one from an 1894 CB and a checkered one from an 1895 Guide Gun. They all fit 99.9%. I decided to go with the birch 1894 set. All it took to fit the butt stock was some minor filing on one side of the channel for the lower tang and the bottom of the bolt hole to open it up a tad so the bolt lined up with the bottom tang easier. The channel for the top tang was dead on perfect. It took maybe 10 minutes, taking it slow and checking the fit several times to get the butt stock just so.
The pistol grip butt stock would be no different.
The real work was on the forearm. Took a half hour or so to get the lips on each end thin enough to slip into the the 39 receiver and forearm tip. Since your just changing the butt, no need to worry about that.