How much do you think it has gained in value? Figure in inflation/cost of living.
Imho,the miles are high in terms of keeping a cherry for resale in the future. Now if it had 25k instead of 125k...?
Many times I see ads of a GN that was put into mothballs when new,but driven now and then. Say it has 1,500mi. The car was $17,000 or so new. Now they are selling it for $35,000. There is really no gain there. A pretty sorry investment. They had to store a car for the last 27 years. The only fun they had with it is just staring at it. I'm willing to bet $17,000 in 1987 was worth more than $35k is now!
I'd say install your parts,but keep your originals. But there is a fine line there,too. Do I want to put my old,split body bushings back in for originality purposes?? No way. That's an improvement/upgrade. How about my old fuel pump? ..nope. My cracked to pieces bumper fillers??
The line I draw is if I begin to hack at the body or frame.
Don't hold onto it for investment purposes. Invest in something else. If you plan on an easy resale,then sell it while it's original. It's a clean slate. Clean slates are desirable,but not exactly worth a whole lot more.
When I first searched for GN's,you wouldn't believe the cob-artist cars I went and looked at. No record of what was done,poor choice of upgrades done poorly,50lbs of rubber caked under the back of the car,massive oil leaks that looked like they had been leaking for years,hacked harnesses...etc. Kenne Bell?? Who the heck is that?!!
Seller: "It's fast. It does 11's."
Me: "Ok,what was done? Nothing looks original under the hood here."
Seller: "Ummm...the previous owner didn't keep any records of any work. I don't know much about it,either. He said it has a cam..." Asking $11,500. Mileage was sketchy. It stunk like b-o. Half of the interior missing.
I left.
Then I found the one I have now. $7,800. 75,000mi Bone stock. Boy am I glad I didn't keep it that way! I'm having fun,and have no plans on selling.
Either sell it now or install your parts and have fun. ...but if you sell it,you'll have to get another one because you have parts.