ok.. say i buy a commodore station wagon, and it had a full conversion done to it so it has no back seats and its a panel van technically taht someone was using to courier stuff or something. if it is completley engineered and its legal with the RTA etc how do the dbdrag ppl see it? if i then fill that whole back sction with gear and i'm in say S or SS 3-4, and not extreme.. can i do that??

i'd need a full list of mods to comment further
but in SS there are few regulations on panel/bodyworkmode rear of the b pillars,
having a wall means most mods in that area don't provide benefit. filling the rear of your car shouldn't be a problem, unless there were other mods done that you haven't mentioned.
you would not be able to use the area where the rear seats should be, and i believe they would need to be installed to technically qualify for street class.
i also believe there is a rule about commercial vehicles , panel vans and vans, being outlawed from street class, but utes qualify for street class.
(maybe this was just a discussion on a rule that SHOULD be in place)

the RTA's version "street legal"
and dB Drags's rules on "street legal" are COMPLETELY seperate.
the fact that dB Drag is a US based organisation should highlight that

It will likely be SS wall legal, since the mods were done above the window line, but behind the B pillar..

this is strictly hypothetical btw... but i mean that there are no back sets, and basiclaly everything behind the front seats is... well... flat... and this modifications was not initially done fro spl purposes...

as long as it isn't extremely modified, like being "stretched" or anything..

when you say "flat"
you mean the floor pan has been modded?
or it's relatively flat, as the seats have been removed?