Sorry I cannot give you the numbers you asked for. However; for my Case 830, the repair manual lists the free length, Spring pressure at two different heights. The manual also specifies what the acceptable range of values are. This data is in the Specification Section of the repair manual.
If you do not have a repair manual, try asking your Case dealer if you can look through his. Our Case dealer (Aldermans) is absolutely great about letting customers look through their shop repair manuals at his place of business.
Hope this helps. Let us know how youi make out.