According to the Whiting Crane handbook, for 300 ton crane with the follwoing qualifiers:
1. Span of 70 feet (nothing in the span range that you asking for)
2. Has 50 to auxiliary crane
3. Based on C class service
4. Crane can be pendant or cab controlled.
The weight of the trolley 170,000 pounds
The weight of the Crane is 390,000 pounds
Wheel load 100,000 pounds without impact!!
The required rail is 175 pounds (this is pounds per yard!!!)
I have various dimensional facts that would be required for building clearances, etc.
This handbook is very valuable and it is out of print. Give me you e-mail address and I will be happy to fax you the data sheet.
I hope this helps.