Sounds like you have a nice car, I would say at under 50,000 miles you should get at least $3000,00 for it. Even withount the T-Tops, that leaves a LOT OF LIFE left on a Z. I don't base this off of any facts, just an opinion. I see them go for $3000,00 in worse shape with more miles than you described. 1 Owner, and under 50,000 miles is very good.
Check out www.kbb.com (kellie blue book). It all depends on the market though. Some who really wants it might give you more. I am thinking about buying a 1983zx, but i don't want to spend more than $1500 because i only want it for about a year. They want more, but if i can't talk them down I think i will get back into my car. But your car sounds good.
I purchased mine w/130 thou on it for 1750. They seem to hover around that price in my area. Mileage doesn't matter in my book unless you plan to preserve it, aka do not drive. If you want something to drive and play with you can pick up a decent Z for 2 grand, at least in North Texas you can.
$3000 sounds cheap. Condition is the driving factor. I shopped for a lot of Zs in North Texas, and the sun had really taken its toll. If your car LOOKS like it should with 46K, it should command a lot more. How hard is it to find a car with a perfect factory dash? Perfect everything? I paid $10K for a car w/ 14K miles. I'm not happy now, because it has an idle problem (as most of you know) from being stored I haven't tracked down yet. But once I find it, I'll be quite satisfied. Before spending that money I looked at alot of Zs. Two years ago Nissan in my hometown had an 82 base model with 14K miles they sold for $14K. At 45K, the price would be considerably less, but if the car is perfect, I think you should get at least $5K, but probably not $6K. I'm not sure though, since it is a base model. Of course, if the dash is cracked and there are other problems, that will knock down the price. Kelley Blue Book isn't designed for special interest vehicles -- because of the low milage -- that have been taken unusually good care of.