Alpina is very thorough
I had an old BMW e12 chassis and they did great work. When I got my W126 and asked for an estimate an work to be done, they told me to save my money as the work would be too costly. Honest in my opinion and I wound up doing the work myself. Another guy in Napa I've had good luck with (for minor repairs) is Eurasian Autowerkes on the corner of Soscol and Third ST. They seem like stand-up guys and their shop is clean. I've heard good things about Napa Autowerke on Yajome street although I have no experience with them.