How much rust is too much?

[special-K]

I have gone out west and brought back many a rust free truck. It's not a matter of cheaper,it's a matter of having a truck with all original metal for me. You can buy a cab back here for what it costs (or less) to travel out there and back to buy a truck or having it shipped. You can have a cab repaired for what it costs to buy a rust free cab. Shipping just a cab is about out of the question for cost as well as handling issues. You may be doing a lot of dent repair when it arrives.
Very few trucks have too much cab rust to repair. I would replace the entire bottom of a truck as soon as rockers,outer floor,corners,supports,lower kick panels... It's not really more work for a larger area of "all new metal". I shy away from rusted rain lip/header panels and cowl rust (which I find a lot of western trucks have hidden due to the sun cracking out the seam seal and dust accumulation in the cowl bottoms) and cowl rust. Those areas hold moisture between panels and are hard to get it all and have it stay good. The cowl is designed to handle water. Water "will" get in there and the question is will your repair allow it all to get out.
When you bring a truck from the dry west to the humid parts of the country,rust that has been on the backside of panels all these years will come alive and start showing it's ugly face if it's not a garage kept truck that sees little to no rain. Even still,there's more moisture in the air and the cooler damper months leave things moist for extended periods. When you've repaired a panel,it's a chance to protect the backside better than it was from factory. It's all about "how" you do the repairs.