Roy,

What I did is flush out the tank with water so that there are no gas fumes. Then I cut it in half with a cut off grinder with a thin disc. Cut around the factory weld seam on the bottom of the tank. After you get them apart sandblast both the insides and outsides of each half. I found a bunch of pinholes in mine so I used POR-15 putty to fill them in. Then I coated the baffles and the rest of the insides with fuel tank sealer up to about 4" from the edges. You leave it clear from the edges so it won't burn while you braze it back together. I then brazed the two halves back together doing a couple of inches at a time and moving to different areas to keep from scorching the sealer. Also wipe down with a wet rag to keep cool. Pour in the rest of the sealer and slosh it around to coat the rest of the insides. I've done 3 or 4 tanks like this in different cars and they've all held up fine.
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Bill (63 P1800 - 69 Triumph GT6 - 74 Triumph Spitfire - 79 Chrysler Cordoba)