What kind car did the other guy have? Was it really a sports car?

It was a Pontiac GTO, convertible. I'm guessing it was a 1965 model, as this episode aired in very early 1966 unless I'm mistaken. Powerful engine, likely well over 300 horsepower. The U.S. muscle-car era was arriving!

I think in one scene at least, you can see the tires have red striping instead of the more common whitewalls.

You're correct that the car was referred to as a sports car in this episode. I think it qualifies easily -- it was certainly one of the more sporty cars Pontiac ever offered. I'm guessing that the GTO became a cousin of the Chevy Malibu and/or Buick Wildcat and/or Olds 442? GM shared a lot of body styles and parts among their brands. (I'm a little more familiar with their later Pontiac LeMans, which was clearly related to the Buick Skylark, Olds Cutlass, and Chevy Chevelle.)

Ok definitely a sports car.

This episode (The Wheels, S6) is unusual in that Linda June apparently is not given a surname. Usually on M3S, a character that is important to the story is named in full. (Heck, even when Ernie mentions an unseen classmate, he usually gives her name fully.)

Sherry Jackson is gorgeous; I’m tempted to say that she’s at the apex of her beauty in this episode. But a full decade later on shows like The Incredible Hulk (guest), she’s still quite hot. Regardless she’s a very good casting choice here.

Just for fun, I thought we'd take a look at Sherry's outfits for this episode. Her skirts I believe are best described as pencil skirts. There is very little variation for her lovely dark brown hair, except as noted.

In her first scene - long-sleeve red sweater, grey skirt to mid-kneecap,
and black patent-leather pumps:
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Sherry's 2nd scene - brown top, hounds-tooth jacket, yellow/tan skirt covering
most of the kneecap, and tan pumps. Large handbag, and wearing a gold necklace
with a round medallion:
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In Sherry's 3rd scene, not pictured: short-sleeve red top, blue skirt covering
the kneecap, and open-style shoes. Small handbag and same gold necklace.
At scene's end she has some white flowers in her hair.

In Sherry's 4th scene - short-sleeve collared blue top with previous grey skirt,
same open-style shoes. Same small handbag:
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Sherry's final scene, not pictured: long-sleeve brown floral pattern dress,
with double gold necklace. Noteworthy that a dark color barrette is clearly
visible for the only time, placed near her left ear in line with her eye. And
there is a tiny glimpse of a small diamond-type earring in her right ear.
Really stunning, it's a shame that the scene is darkly lit and we don't see
Sherry's full body.

This episode (The Wheels, S6) is unusual in that Linda June apparently is not given a surname. Usually on M3S, a character that is important to the story is named in full. (Heck, even when Ernie mentions an unseen classmate, he usually gives her name fully.)

Sherry Jackson is gorgeous; I’m tempted to say that she’s at the apex of her beauty in this episode. But a full decade later on shows like The Incredible Hulk (guest), she’s still quite hot. Regardless she’s a very good casting choice here.

Yes she is! On Danny Thomas show she was just a pre-teen.

I think Parmenter would have won her over, in the real world.

Just a few years later, circa 1970, here is how Sherry looked on Make Room for Granddaddy. So very beautiful:
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I would really like to see the full Make Room for Grandaddy season.

That's a great picture of Sherry!

Here's a great look at lovely Sherry Jackson on The Rockford Files, Oct. 1975 -- really hot in a bikini!! :)

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How beautiful she looked on these shows! I love seeing her in her black pumps on M3S, very proper and at the same time remarkably sexy!