So, I just had my little round with replacing both front brake calipers and pads...
Here's a little scoop of info:
My 4 runner is the limited with 17" wheels, the calipers I had were stamped 13WG which are the expensive ones. I went to autozone and looked at the 13WL calipers and didn't see a bit of difference (other than they're half the price). I even made many measurements with a micrometer and everything was within 1mm, mainly 1mm smaller on the old ones due to junk build up. So, I took them (mainly because that's all they had and I was in a time crunch to get the brakes done) and installed them.
After bleeding brakes and test driving... everything works fine. No difference in braking power or the feel of the brake pedal. I thought maybe the internals on the calipers are different, maybe something with the pistons? But they fit fine and worked great!
If you have the 13WG calipers, you can use the 13WL calipers. The stamp indicates the wheel size and rotor size but at least between the 13WG and the 13WL there isn't any difference except the cost.
Anyone have any other input on this or comments? I am curious to see if anyone else has used calipers that had different stamps.
btw: Total cost for all new parts including pads, fluids and brake parts cleaner was just under $200.