Dont junk it yet
i know this is a dead thread but i finally diy repairs my rusted crossmember and it is not a bad job plus i guarantee my fix is stronger then factory first go buy yourself a pipe from a welding supply co. the dimension are 2.3/4 by 45.1/2
also i know the crossmember in your truck is arched it is not nessisary to be i used a straight pipe and its much stronger now heres the answer to one question i had before i did this job is the frame weekend without it , answer is yes with my pipe only a few inches threw one side i could easily twist my frame by hand was incredibly scary to think that i could have toasted my truck , now first thing first my truck i performed this on is a 99 silverado 1500 ext cab
lift your bed off i did this with two people we both put our arms together asif we were genies and placed them under each wheel well one person on each side is doable but yowl hurt in the morning the skirts of your bed are strong enough to place it on the ground or even just leave the front of the box leaning on the rear bumper without having to put blocks under the skirts won't cave , now remove whats left of your rusted crossmember mine just meant unbolting from shock and tossing it in the garage you will need to cut around the original welds of both the tank mount and the shock mount (sawzall) works best trust me tried a air cutter just vice and slice.
then grind the hell out of the outer edges get yourself a extremely clean welding surface exspessially if you suck at welding like me
get them nice and ready to put on new pipe now take your pipe and slide it threw the old pipe that is still intact threw the farm rails i used a 4ft maul for this its a tight squeeze but any smaller then 2.3/4 is to small and larger won't fit.
grind down the edges of the old crossmember weld your pipe in
again it will look like crap if your like me who cares
feel around where your shock will be most comfortable and also eyeball the other crossmember to make sure you get the mount welded in close to oem and mount your tank bracket as close to the tank as you can without killen yourself ( you are welding)
replace shock and strap your tank until you can get a new factory strap i assume its rusted out with your crossmember and slap your bed back on if you have any questions or need photos please feel free to reply to me i will try to do my best
i only wrote this and actually only joined this forum because i searched every where and found nobody with a solution or any help at all on repairing my old truck so i hope the next guy that searches finds this it was a 5 hour job flat with two guys you will need a 18mm to remove the underside bed bolts there are 4 each side and a extension to gget them out also reccomed impact to remove them i used a corded electric impact a cheap harbor freight one did the job fine. you can defiantly fix yours don't junk it yet
also thanks to my buddy dave.w if he finds this and thanks to dave.l for letting me use his garage and tools