Squared in the valley its a Teksid, diamonds it's WAP
It's also worth looking at the casting number. The '96-'98 Cobra block has a casting number that starts with "F6LE..." (same for the Mk-VIII). There were also '99 blocks, which have a casting number that starts with "XR3E...". Both versions also have the square pattern in the valley vs. the diamond pattern found on the WAP blocks.
Not sure how significant the differences are in the '99 block, but a lot of '01 Cobra's turned up with them, whereas the earlier block was only found in the '96-'98 models. It is generally reported that the WAP block was supposed to be the "only" block used from '01-up, but apparently that isn't the case.