In all honesty between 15-20 would be a realistic price, closer to the 15 though. This all depends on how quickly you need to move it, so the quicker the cheaper.
I think people need to realise that the crazy silly money that was going around 4-5 years ago has disappeared, these cars were getting 20 then so to ask 20 now might be a bit much. That's not to say you might not get it so if you want give it a go but remember it might be sitting around for a while. One of the guys here has a pretty shmick 260 that's been going for a while and he's dropped his price a couple of times.
Wothout having seen full exterior and interior pics I can only guess that it's a daily or regular driven car from your description which means stone chips and maybe some faded paint. You did mention that the tailgate has some cracks in the paint, probably more due to the previous paint work thatn anything else but this means that there could well be more waiting to show its head. By no means am I suggesting that there's anything wrong with the car but in a daily/regular driven condition 14-15 might be closer to what you would get.
I recall a white 240 a few months ago around Werribee going for around 17, it sold but even at that price it was their for a while, also I just had a quick look on carsales and all the 40'z on their are around 18-19 so if you need to move it then putting it in for 16 would certainly get you some attention.
Oten it's easier advertising at close to your bottom dollar so that prospective buyers can feel like there still getting to haggle you down and feeling like they won, very important quicker sale. So if you'd be happy with 15-16 then put it in for around 18, oh and if they want to go further then start removing things like rego or any add ons like wheels, they soon come around.
At the end of the day though if people are coming up to you then ask them what they'd be willing to offer, if it works then go for it.
