Ok, for my pennies worth; I ground down the welds with a flap wheel, often this can expose pin holes that would otherwise go undetected. Whilst in a perfect world (or a more professional weld) there should not be any pinholes, I found that after shotblasting they were quite numerous. I include those voids that do not penetrate right through the steel in that category too. It is not always possible to see clearly.
I would advise against using body filler directly on any welds that may contain pinholes as it is porous and eventually will allow rust to develop. I used JB weld to be sure on any exposed welds that could not be sealed with seam sealer. I don't see any reason to use body filler on anything except the exterior paintwork. I found that the stone chip was enough to give an acceptable finish to "hidden" areas, for instance on both sides of the floorpan. Where the welds are only accessible from one side, thorough waxing inside of the box sections should be enough to protect the from behind.
For welds like the door skin where there is a but weld that is directly under finished paint I was very careful to try and avoid or repair any pinholes. On the underbody structure there were voids in some of the plug welds and these were filled with JB weld prior to seam sealer and stone chip.
I hope that together with the pictures on my restoration thread this is of some use.
For interest I have just done the first 500 mile service on the traveller and it spent a rainy day today at the biggest local classic car show (over 700 cars?) here in Cumbria. It was on our branch stand and attracted a good deal of interest from visitors
