Good luck building a .318WR on a Spanish action. Please keep us posted with the progress of the build.
If you want an expert opinion we are incredibly fortunate to have one of the finest gun makers on this forum. Joel Dorleac of Dorleac and Dorleac answers emails. I have contacted him several times and have gotten quick and courteous responses.No one I can think of knows more about Mauser actions and will take time from his busy schedule to answer questions.