As I remember the rail we found in use was mostly 60/65 lb and some 90 lb. Obviously the 90 would be better, but I think they would accept either.
If the rail is the larger, you can mill the ties, like we found around the Masonic Park area, and lower the rail to match the smaller rail on the outside.
Would be so neat to see 20 miles of dual gauge track in use.
They would be able to do the area from South Fork to Wagon Wheel Gap (as I remember about 16 miles, don't quote me) with little problem, as there are no switches in that area. At Wagon Wheel Gap there is a passing siding that would need the extra frogs and points.
Let Don know if you can find any rail. I am sure the transportation can be worked out. My Dodge Caravan can probably carry at least one at a time.