In the studio you always have to decide which of the two will occupy the lowest position when you're EQ-ing.
Live, I think the sound he's going for just won't work. A big boom might feel great, especially on its own, but you'll get all rumble and no clear start or end to the note. That's why you're having to use a noise gate.
In Led Zep, remember that JPJ had a smooth mid sound with not much low end. Somewhere one of you will have to compromise your low end. I personally think that bass should go lower than the kick drum. But then I'm a bass player.