I have a 12 year old mountain bike that I'm riding again and making more roadworthy. So far, I've gone through and adjusted the seat and handlbars to a comfortable position and switched the 2+" wide tires for some 26"x1.4"'s. So far it has helped and I can comfortably ride on the bike.

The problem I'm running into is that I have a Rockshox Jett T2 suspension fork that I would like to lockout or replace with a rigid. I measured the fork and bike. It's a 1 1/8" threaded with a 120mm smooth steer tube and 25mm of threads.

Questions:
1. Is there a way to mechanically lock out the existing Rockshox?
2. If I decide to go with a rigid fork, what measurements am I looking for online to order one?