Hello,

I have a few pin holes of rust in my bed right above the rear 19 gallon tank.

Would it be safe to weld shut the holes with the gas tank installed or is the tank too close to the bed?

 

As long as the tank isn't rusty and the hoses are tight, you should be fine. If there's any doubt in your mind, put a fan under the truck and blow across the top of the tank. This will blow any stray gas fumes away. There's a good 3" between the bed floor and the top of the tank and there's two layers of steel in between the bed floor and the gasoline.

 

Too close to the bed in my opinion because of the chance for fumes. On most later-model EEC tanks, the vent valve is directly on top. The sending unit opening faces upward too. If either o-ring is compromised at all, there's a good chance for a pocket of fumes to collect directly underneath the bed. Dropping the tank isn't the easiest job in the world, but it's not overly difficult, so there's no point in risking it. Others may have different opinions though; mine is just one.

 

2x with fumes and fans.

Slide/insert a non-conductive material, like thin plywood, as a backer behind the holes lest ya inadvertently strike a bead through the bed and onto the tank. That would take talent though.

 

You may have reasons for not doing this, but the best way is to pull the bed. Then you can get at all the problem areas safely.
The biggest problem would be getting the old bolts out.
Having said that, I have welded around gas lines and such before and put a piece of insulation and metal in between the problem and the torch.