Depending on the year, your WW was either equipped with a Happijac or RBW bed lift system. Happijac has rails that run almost floor to ceiling and is chain drive. RBW's system used nylon straps and floated against the side walls with rubber wheels.
If you have the Happijac system installed, you can fabricate the bed platform (I'll be happy to send you drawings) if that's all you're wanting. If you want the sofa/bed combo, then yes, Warrior Lifestyles is the best option.
If you have the RBW bed lift, the sofa/bed option was installed on a specially designed frame. I'll check drawings to be sure.