Do the existing struts have labels on them? I replaced mine with same size/weight as label...think it was 120lb. We also added a latex mattress pad. Now I don't have to ask my spouse to hold up the bed when I want to get something from storage.
I also replaced all the struts on my outside storage bays. What a difference! There are several online websites...just do a search. Can't remember the name of company I purchased from, but it was the only one that carried all the different sizes/weights that I needed.