What to look for in a NC Miata?

Wife had an '06 back when she was the girlfriend,  sold it for her CX5 after 40k or so.  We are lightly toying with the idea of getting one, I figured I'd see what (if any) trouble spots they have now that they have been around long enough to be out of warranty 

Since her soft top was slashed open once, she very much likes the hard top convertibles, but I'm 6'1 and am concerned I'd never fit in one.

Manual, of course.  She'd like bluetooth compatibility for the radio as well.  I'd probably steal it a couple times a year for auto cross or something similar

Coolant tanks came up a lot when I was looking. The 09 and later cars seem to be worth it for the extra revs and suspension changes. 
 

We've got three of them in the fleet, two of which are PRHTs. They've been problem-free. People make a big deal out of the coolant expansion tanks but they're like $65 for stock plastic ones that will last for years. I certainly wouldn't pass on a car just because you think it needs to be replaced.

I looked into NCs before buying an NB. I'd replace the coolant expansion tank right away. But it's an immediate failure item so if the engine runs it's fine until it goes. Then you 2.5 swap, lol. Or replace the tank and it's fine. The aluminum tank is $200.

09 + got some gear box changes too, taller 6th and fixed a weak 3/4 shift fork. 

Savagegeese did a great series on the Miata and included some good technical stuff for those that enjoy the details. He talks about the 09 updates which is why I mention it. 
Seatbelts can fail to retract sometimes. I couldn't find much to look out for and I spent a lot of time looking into them. There's no real gotchas. 

Glad to hear they are relatively bulletproof outside the expansion tank.

Anyone have any info on the height issue with the hard top?

We have some content right here on the site that could help:

GRM's NC Mazda MX-5 buyer guide.

NC buyer info from Mazda Motorsports. 

2.5-liter conversion article. 

Turbo comparison article. 

If you're thinking of autocross, it's not a bad idea to consider what class you want to compete in, before purchasing or doing modifications.

It's really easy to modify yourself out of street class. As discussed recently, even an aluminum overflow tank will put you in a modified class.

In reply to Floating Doc (Forum Supporter) :

If I'm doing autocross with the wife's car, it'll just be to get out and do some fun driving.  Won't be to try and be competitive.

Floating Doc (Forum Supporter) said:

If you're thinking of autocross, it's not a bad idea to consider what class you want to compete in, before purchasing or doing modifications.

It's really easy to modify yourself out of street class. As discussed recently, even an aluminum overflow tank will put you in a modified class.

Looks like my STR car is now in modified. Jesus the SCCA has some really berkeleying stupid rules. For years, didn't a non-OEM oil cooler do the same thing?

"I'm sorry sir, your car losing coolant and toasting the motor on course is a performance advantage."

Not that I would be looking to be competitive, just occasionally go out and have some fun.

z31maniac said:

Floating Doc (Forum Supporter) said:

If you're thinking of autocross, it's not a bad idea to consider what class you want to compete in, before purchasing or doing modifications.

It's really easy to modify yourself out of street class. As discussed recently, even an aluminum overflow tank will put you in a modified class.

Looks like my STR car is now in modified. Jesus the SCCA has some really berkeleying stupid rules. For years, didn't a non-OEM oil cooler do the same thing?

"I'm sorry sir, your car losing coolant and toasting the motor on course is a performance advantage."

Not that I would be looking to be competitive, just occasionally go out and have some fun.

A new OE coolant tank is fine.  A non-OE tank is not.  Why?  Because the non-OE tank could provide an advantage.  If you can prove that you can't get a new OE unit, then you can likely get the aftermarket one cleared.  More than likely, at a local event they wouldn't care too much.

The aftermarket oil cooler could also provide a performance advantage.  Similar deal to above, local events likely wouldn't worry too much about it.

While the rules are sometimes poorly written, they have to cover a wide gamut of vehicles so the rules can seem silly or arbitrary in some cases depending on how they end up being applied to a specific platform.