Anyone know a web site where I can check what the numbers on my main bearing and big end bearings mean. I've google all sorts but have come up with nothing except engine casting numbers etc. Didn't want to have to remove the crank fully just to get it measured up as the numbers must mean something and the crank is fine, the rod bearings are wearing so want to change them and will also change the main bearings at the sametime.

They are all stamped GM along with various numbers.