I have not replaced the F.P. assemblies on my two 700's. I know that many people consider this "ISS" a joke, or at least an inconvenience.... on that I cannot disagree. I simply don't use
the feature. As the bolt assembly is the same as any other 700 (except for the ISS feature)... unless, somehow, it malfunctions... I will simply leave it alone (and save the money that I would need to spend on replacement bolt assemblies). I can't prove it, but I doubt that this gizmo will ever cause any problems. As a matter of fact, I actually ground down one of the "keys" that came with (one of) my 700's... and made a neat little sight adjustment tool.
If you truly desire to replace the assembly, Brownell's has the non-ISS firing pin assemblies for $65.00.