Yes - good point Bones.....otherwise it could get ugly !!
looking forward to the photos Paul - if the header pipes are in good nick, its definitely worth hanging onto them....if the holes on the back are on the 'inside' of the mufflers (generally they are, but not always) - then you may be able to just braze some 'patches' over the holes, and spray them with silver paint ? I have seen a few old Zeds like this, unless you look pretty hard at the inside of the mufflers, this repair is good enough for a daily runner - not really up to scratch if you intend bunging the bike into any show'n'shines though.....