Basically, the cleaner the parts are, the better the weld will be.
That goes double for the fit.
If your k-member is out, it would be a lot easier.
Take some time and re weld some of the crappy factory welds as well, some were just barely good enough to pass. Pay special attention to the holes where the torsion bars go in as well as the steering box mounts.
Look at my build thread, i did a lot of extra welding on my k-member while it was out, and have lots of pictures.
