I believe you should be guided in your decision by a chain stretch measurement. If it's still close to within spec, you might decide to revisit the chain at 125K.

The rails, yeah, absolutely do the rails. Too many horror stories about brittle old rails getting fractured and pieces being processed through all of the valvetrain on that bank. Yikes!

I think the rule is that chains rarely fail without giving some warning first, like slap on startup. Rails can and do fail without any symptom.

s/b