When you say you will be "resoldering" them, do you mean you will be refilling them with lead?
In my case I have done a lot of chassis stiffing to include welding in the K frame, reinforcing the shock cross member, US Tool sub frame connecters, 1/8 plate home made torque boxes, a 1/8" boxed and welded radiator support (you can easily tow the car from this), rectangular inner fender braces, etc. When you jack up one corner the entire side lifts.
I agree that both the quarter and the roof are off in heights and was planning to use all metal to fill this gap as well as blend it all in.