Some SP-10 parts are interchangeable, some require fitting, and some aren't. I don't know which are which but my gunsmith does.
What is the problem with the firing pin? Depending one what it is, it could be as simple as a good cleaning that could fix it. If it is a spring problem, Wolff has pretty much every spring imaginable. I replaced all the springs in my Mag-10 with those in a Wolff package and the gun has run flawlessly with steel loads since.
