My original bathroom hardware was all Price Pfister brand, and so to avoid having to change the valve stems I thought I would just use more Pfister fixtures. Unfortunately I was out of luck. The valve designs I had were considered "obsolete" so none of the new trim kits I bought for the shower and roman tub would fit.
I tore off the entire section of green board that was in front of the tub, and I will replace it with cement board.. may as well do it right if I am going to do it.
I had to tear out the old valves and insert new ones. This was a pain because they use copper connections.