Several people have already answered your question and expressed doubt that you can get an 05 LS430 for $1500 over invoice. I have, 99LSguy has, Ikirschner has, FlintUltra has, blake 918 has, ronsadvice has and he offered to help you try and you turned him down, Unlisted has, silermate has, MikeP has in other threads.
I'm starting to question whether or not you actually want our advice or if you just need someone to agree with you.
The fact of the matter is your G35 and the LS430 are totally different buying experiences. The G35 is an entry level luxury car, almost $40,000 cheaper than the LS you're shopping for. Infiniti has much lower demand than Lexus and much lower resale value. Infinitis will ALWAYS sell at steeper discounts than Lexuses. The LS is the flagship model, most dealers don't even stock UL cars they have to be ordered so you're not "rescuing" a salesperson by buying an LS like you are by buying a G35 off the lot. Its just a totally different strata of car and a different buying experience. If you offer a dealership $1500 over invoice for that car they'll laugh at you. Like we've said before $66k is an excellent price on that car. If thats too much then you really need to look at a different car.
I apologize for getting frustrated but we're trying to help you and you refuse to accept what we're saying and keep asking the same question over and over.