I added washers to the inside of one k-member. I don't think it's really necessary if you just add weld around the tube.
Separating the two halves is A LOT OF WORK. Lots of spot welds and several places of mig weld. I did because the k-member I was working on was tweaked bad from an accident. I bought it to find out IF I could fix it. I felt that there was no way that it could be straightened as a complete unit with the tools that I have.