What should I pay for vk executive bit rough body wise but does not appear to have rust trim also average 6cylinder auto no air no power steer

I think crowe is on the money - but if it has no rego you'd halve that figure. It also depends on what your location is. If it's in Sydney or Melbourne, people struggle to give them away, and they're often sold for a few hundred $ for rough ones.

Unless it's a Brock, a Calais, or a V8, then it won't be worth much at all, regardless of the condition.
I turned down a mint one for $1500 with 6 months rego that was offered to me a while back, and it took him weeks to sell it.

On the other hand, a mint exec or SL with Cerulean trim in it recently went for over $2K as a parts car for a VK SS restoration, so it's hard to pick the market.