Originally Posted by Slowcrash_101

In the service manual you'll see that there are main bearing codes and rod bearing codes(located on the block and crank respectively). These codes correspond to one of 5 bearing colors. Each color is a different thickness bearing material. When you remove material from the crank to repair a journal, the journal becomes smaller, so you use a slightly thicker bearing to maintain proper clearance between bearing and journal. The clearance is checked by using green plastigauge.

First you try by using a bearing with the same color as the one you're replacing. If the clearance is with specs you're good. If the clearance is too loose use the next size up to take up some clearance.

The manual lets you go up one size before telling you to chuck the crank. I wouldn't weld material on the crank and try to clerance it, personally.