D1.5 has a few things to watch for when qualifying welders:
Clause 5.21.3 Base metal has to be an AASHTO approved steel as described in Clause 1.2.2 or the WPS(see Clause 5.24.1.1)
Clause 5.24.1.1
If the project has steel with 90ksi yield or greater, it makes you qualify on base metal meeting the same specification as the steel for the project.