Is that more difficult to do than emailing him a question? 
There were some 240/260/280 Z convertible conversions.
I think a 280Z convertible conversion would be very close to what you describe.
I just asked him if he drove a black convertible, without elaborating. He doesn’t; he drives a white Altima.
The search continues.
Don’t ya’ll be dissing my TR-8 and Opel GT. My big sister gave me hers, and I still have them!
This may seem obvious to a self-proclaimed gearhead, but how about a Mondial t ?
Pointy front, square back, horizontal lights, topless…
If so, you realize you’ll have to turn in your GH card, and your Mancard status will be under review.
Can’t believe it, but I just passed a Nissan 240 SX convertible today. No badges, no lettering; looks like it just had new black paint put on.
Eh?
Marcos Mantara? Hard to tell from that image but like most British shed-built cars of the era it has a Rover V8 under the bonnet.
Good candidate, but I don’t recall the deck lid rounding in like that - more square across and fully shading the taillights. (The lack of wraparound tail lights is one of the things that makes me think pre-80s era.)
Nothing so gorgeous, I’m afraid. Part of the problem is that the Mystery Car is pretty dull, like every other wedge-convertible of that 15 years or so.
I hope to run across it again before the end of summer, and I will make an effort to chase it down and get an answer.
I’m confused now. Did it have pop-ups?
Rover bought their V8 from Buick. Shoulda got their electrics from Delco-
I honestly don’t know. I didn’t look right at he front end the first time, and while I can recall the flash of “hello” headlights the second time, the configuration didn’t register.
I’m going to have to find some way to flush this mystery car from hiding… 
If you are something of a car guy, perhaps it will come to you if you just see the name.
Otherwise, you’re in for some clicking. Click on “Select a Make” and browse the manufacturers, both current and defunct. Or search all 1970’s convertibles.
Report back.
I didn’t see any name or badge - I think the thing was customized or dechromed a little. And I can’t make any of the details add up to a car I know, which is saying something. (There are many cars of the last ten years I can’t ID fer squat… but get back about 15 years or so and there aren’t many I can’t nail from a partial shot.)
I might rummage Hemmings, though.
So says the guy who drives his sister’s Opel GT. 
That’s a Celica Supra, back then the Supra was just an option package on a Celica.
And it’s yellow…
I have been waiting all summer to see this car again, and it passed me when I simply did not have time to turn around and follow it for a bit. I am about 99% sure it’s a late 1980s Supra; all the details of the long, squared-off wedge shape match. However, my limited searching hasn’t turned up a convertible of that body style and approximate year. Given that it’s blacker than black from end to end, with a generally customized look, I suspect it may be a conversion.
I will keep looking for an image and see if I can corner the beast before summer’s over.
Where it not for the big V8 engine requirement, I might guess the Nissan 200SX from the early 80’s.
Like this?
If that’s not it, I can’t imagine what would be. Specs?