I'm not sure about this either but I think Greg Cox's novels about Gary Seven are all consistent with The Peacekeeper from DC Vol 2.
Not entirely. They do both use the same name and background for Gary's employers (the Aegis), but "The Peacekeeper" asserts that Kirk hasn't met Gary since "Assignment: Earth," which conflicts with Assignment: Eternity
and The Eugenics Wars
. However, I just disregard the couple of panels in the comic where that's asserted, and that way they can fit.