Those both come in spacing for either 3.5" or 4" CTC b/t the studs. If your stock doesn't have any...just get the shortest one possible, and go to your hadrware store and swap the hardware for wood screws. This is what I did for my .22lr...works perfect.

JYD #121
The chief cause of unhappiness and failure is trading what you want most in life for what you want at the moment.