JLS,
This subject has come up before, and here is a link to it.
Bed Gas Struts
If I were you, I'd call PI and talk with Donna to see if they now have the 100# struts Bryan mentioned in his comments. Worse case scenario, take the old strut to the local auto parts store and match up the physical dimensions and get as close to 100# test as possible. Also make sure you don't have anything on the top of the bed when lifting. A little something at the foot end of the bed really feels heavy and hinders the lift! (mechanical disadvantage) Tom