I saved the spring info Richard provided above, since I'm planning on running this mild mannered cam in a new motor. Recently I posted the same spring specs on a Y forum. The response was that the pressures were high and the dual springs unnecessary. Guides would reportedly require machining for inner spring to go on.
One respondent who races Y's has a motor with a more agressive cam than the 260, which has been above 6500 rpms many times, no valve float. It has springs that are 93# on seat and 250 lb open. That is getting very comparable to the spring specs Thunder1957 first mentioned. The pressures also are supported by data in John Mummert's adds which appear in Y-BLOCK MAGAZINE, as well as Schumann Sales. Both businesses cater to the Y's Guys.
The stronger the spring, the higher the rate of cam and lifter wear.