When you put Commodore (VB-VL) seats into HQ-HZ only 1 seat bolt aligns (front one closest to sill). You have to drill a hole for the other front bolt right next to the other side captive floor nut (by right next to I mean it is that close that you don't need a spanner on the nut you put in as its flat will be hard up against the existing captive nut). If you use an original captive nut that you have chiselled off a rusty donor floor and sit it next to the existing one it will look factory, and the hole is drilled through the floor and the underfloor member. The problem arises with the back 2 bolts: holes go through single skin un-reinforced steel.

With WB seats (or Commodore seats with WB rails) bolts on one runner align with existing captive floor nuts (outmost - closest to sills). You do the same for the front other side as per Commodore seats. And then the rear other side is done the same as the front. You end up with holes through where it should be (through the floor and an underbody member). What I have done is simply tack weld the new nuts to the existing captive nuts. Looks factory once done. Looks even better if you grind off the inner original captive nuts, drill a hole in the required place and weld in a donor captive nut in the right place. Just put some black goop in the original holes. Then your HQ-HZ floor is basically as per WB.

If I get time i'll put up a photo of WB runners next to VB-VL runners. You'll see they are the same thing, just WB have extra outriggers spot welded to the Commodore runners to pick up the WB floor holes.