Need a little frame advice

[69chevy lwb]

So I just finished up shortening my 70 c10 and noticed the wheelbase is pretty far off on one side. But the wheelbase is 115-1/8th" on both sides. So checking for square I found the frame was 1/2" out in 3' so it's pretty bad. At first I thought it was my doing but I looked at a picture of it before I started and it was terrible then too. So I know I messed up not cross measuring when it was apart but does anyone have a simple solution to pulling the frame back into square? I hate to move the crossmember because I will have an unequal wheelbase and the c notches will be misaligned. Any advice would be appreciated!