Sir, as a proud owner of of an 87 GN from day one I can tell you that for 6k you won't get much of a car. If you only want to spend that much I would recommend a T-type which is the same car only in diff. colors . They can be bought for much less than a GN. I live in Texas and work with a gentleman who has ten sitting outside his shop at any given time to be worked on or modified.
My GN , which is heavily moded, will easily run 10's in the quarter mile. If you think a SHO is expensive to work on just wait till you try to keep the Buick running at tip-top shape. If I were you and you have your heart set on a GN, save another 5K and get one that is solid and newly rebuilt. If you need any info on them feel free to email me. I am a BUick Nut and have been involved with building , restoring and showing them since I bought mine in 1987. I love the car but some days it makes me scream trying to keep it alive and well. Still, the most enjoyable to drive and show.
I don't mean to be a killjoy, but I know what you get for 6k today . You will spend lots of money getting it right. Better to let someone else spend the money and you buy it from them. Just my advice.