Most bolt patterns are 6-6-6, even on 85 lb rail. Common measurements for 75 lb webber bars are usually 6"-5 1/2"-6" or vice versa.
This "new" rail will be enough to last the museum for a few years. As long as grading can keep up, and ties and other material supplied, Dana's well led group of track layers can resume building around 1200' per work weekend.
Although many of our obstacles are closer than 1200', hopefully some can be over come ahead of the track crew.