To me, the first pop is at -3313, -1051. Its the very front spawn point as mentioned in previous post.
3 mins after it has been killed, another pops at -3072, -1552.
So, I believe any of the stonefin basilisks in the front half of canyon can be his PH, except the elder ones.

Basilisk Scale
Lock of Veldyn's Hair
Sand Guard Mantle
Signet of the Mistdragon