have been working on my sons 89 mini which we have just bought, treating rust in usual places and wax oiling as per a brilliant post on box sections. He has removed some of the bituminous sound deadening material in the foot well as it had started to split and the rust seems to be centered around the 3 drain plugs?? Can we just knock these out and replace with new ones, once sorted the surface rust out or do the plug holes need to be welded up? Haven't done it yet as don't have access to welding gear if that is what is required.
Thanks