back half question

so i am building a notch and rails for my 99 gmc and i got them all tacked in and leveled and everything was perfect but i started welding it in and i put jackstands under it to keep it level but when i pulled them out and one side sunk about a quarter of an inch. the main reason for doing this was so my 22's will clear and so i can hang a cell in the back i think besides shimming the bed and tank that is the only thing it will affect but i still want it right any ideas on how i could do it with out cutting it completely out

the heat from welding it is probably the cause of it moving/pulling. since a 1/4" isn't a lot, you could probably just leave it and shim it like you said.

If you or somebody you know can get you in a bodyshop with floor tie downs you can tie it down and then jack the low rail back up level with the other one.

I'd say you would probably be fine how it is man. When I did the hardbody and got everything welded up i was bout the width of a washer from being level anymore. I just adjusted the slack out with a shim when I mounted the bed.

depending on where the tweak started you could cut the top and side welds with a sawzall then jack up the frame rail & re weld it, V it out first of course. This will allow the frame to go straight without tweaking the rest of the frame.