Like Johhny sez- We were just talking about that the other day. After 24 hrs. you can spray undercoating on. Thats what I used after welding on door bottoms. Make sure drain holes are clear when done for Houston monsoons! I added 1/8" holes to what seemed low area of my door bottoms.
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69 C10 longbed: 357c.i. /TH400/3.73s/AC/ beige primer/saving $ for paint
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