whats better for the repair of the common body rot on a late model chevy pick up? Ive got a primer grey 75 Silverado thats just a work truck, but they are really the only bad spots on it. Not rotted all the way through but pretty close... Fiberglass or Bondo?

Since your truck is a work truck... I'd probably go with fiberglass. Bondo or fiberglass wont stick to rust very well... gotta gring most of it away. There is some stuff called "kittyhair" made by evercoat. It is chopped fiberglass mixed with resin, you add the hardener. It gets hard as a rock and bonds excellently. Obviously the best method would be to cut and weld in new metal if the spot was bad enough, but like you said, its just a work truck. One last thing, the fiberglass is waterproof unlike bondo.

Duraglass is good too.

After cutting away all the rust on my 72, I patched the holes with fiberglass. It worked great!!! 2 years and counting with no rust coming through. Now I have to cut all that stuff out to weld in the metal patches.

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72 C/10 LWB 2wd
250 inline 6, 3 speed column shift. Watch for my 72 in the 2001 online truck show.VOTE DUBIE, FOR A BETTER BEATER ;)

duct tape and cardboard hehehehehehe (at least duct tape kinda looks like steel LOL)

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71 Custom/10 lb fleet .040 over 350/th350 good ol 1 wheel peel 3.73 12 bolt 275/60/15 front 31x10.50 rear on GMC Safari wheels
#3 Dale Earnhardt will live forever in our hearts and memories
"THE WORLD'S GREATEST RACE CAR DRIVER EVER"