I have welded cast to steel with a mig welder never had any issues clean it take a propane torch pre heat it then weld it.As far as converting the steering i would rebuild the power assit.As long as the control vavle has been greased theres only two orings inside that will leak.The ram can be resealed as long as the piston sealis good otherwise it can be sent off to be rebuilt.I see where Rockauto has this service.The hoses you can buy adapters to make them convert to JIC fittings then any local hose house can make the hoses.I would just make the hose with no steel tubing.I have made my own adapters by taking a JIC plug then drilling it in a lathe brazing a brake line on it.
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