Thanks for all the info so far, everyone! Good stuff!
The truck is at my garage a few towns over which I really only get to on weekends. I'll see if I can get some pictures, but to my recollection, the majority of the back "wall" is rotted out. The whole front end hasn't collapsed yet, so I guess that's a good sign... Not planning on taking it down the road that way, obviously.
I do have a hefty welder and I'm pretty good with it, I just can't see the extent of the rot in the truck's current position. There's a possibility (being from the land of salt and disintegrating tail gates) it's too far gone, so I'm planning accordingly. If I can save it, I definitely will, but I'm preparing for worst case.
Now on an related note, if I'm going to lower the truck at some point, what are the limitations of the factory crossmember? I'd like to lower it to the point I won't need to C-notch the back. Exact amount is TBD, but just curious what the limit is with factory parts.
How low you can go depends on what you want to do with the truck and your budget. For example, QA1 makes a whole replacement front crossmember to go with their tubular front end with rack and pinion, you can go 8" up front with that setup. With a stock crossmember and stock control arms, 5" is kinda the reasonable limit. You can get 6" with tubular arms and some other tricks. Most guys are some combination of 4-6" up front and 5-8" in the back.
Some trucks can get away with ~4/6 or even 5/7 without a C-notch, my buddy's truck was 5/7 and he said he'd only slap the rails if he added his big cooler to the normal roadtrip stuff.
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I like the peace of mind knowing I can load the truck up and not bottom out, especially cuz I travel with alot of tools on roadtrips, so my truck is notched. I regularly work the truck (sometimes more than it should be) and I roadtrip it all over the country (43k miles in 3.5yrs). I'm ~5.5/8 with stock arms up front, 2.5" spindles with stock springs trimmed a little at a time till I was happy. Rear is a flip kit, 2" shackle, shock relocators and helper bags. Belltech SP shocks all around and it rides great. I can't *quite* get the front end in spec but still get ~25k miles out of the tires, I just have a little too much camber for the highway running we do.
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Top is 4.5/6, middle is same with rallies, bottom is 5.5/8
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