Well there were probably 3 threads just like this.
http://forums.hybridz.org/index.php/topic/90240-798whp-l28et-for-saleyour-thoughts/page__p__855647__fromsearch__1#entry855647
http://forums.hybridz.org/index.php/topic/90210-83-280zx-turbo-798hp-for-sale-on-ebay/page__hl__800hp
And as far as I am concerned 99% of the world measure the after market performance gains in WHP. I know the ad said 798hp but either way there was no proof to back up the claim. As far as you know my stock turbo'd L28 was a 600hp monster too. It did make 334whp @ 15psi so I figure at 30psi I am well over 650whp. So I guess I have a 600whp Z also.
I know I come off as a prick often. I dont always mean to be but when people go around throwing out random estimations as what the car infact does, well, the people that sweat, bleed and spend in order to achieve such numbers dont really care for it.
The car went from a 800hp CL ad, to a 798whp CL ad then finally 600whp all with no dyno sheet or even a track time. Just because you have a fancy build sheet does not mean that you can claim what you want.
That being said your car is definitely and amazing build and I do hope that you can come back and shove a 600whp or even that 800whp dyno right in my face.