I have a 1970 Dart Custom 2 door hardtop. Factory Plum Crazy Purple, with black vinyl top and black bench seat interior. 318, 904, HD suspension, 8 3/4 rear end.
This was the top end Dart trim level in 1970.
On the quarter panel, it has Dart and Custom emblems, in the same location where a Dart Swinger would have the emblems.
Anyone have, or know of another like this? I'd say it must be pretty uncommon.

According to the GG white book, there were 4880 Dart Custom 2 doors built with the 318.

Also, are the Custom emblems used on any other Mopars? It is a rectangular badge with CUSTOM recessed into the surface. They are reproduced, but I would prefer to find originals

I had one for a time. Apparently most Dart Customs were 4 door models, mine was 318/904/8.25, AC, power everything. Woodgrain dash, Custom specific seat pattern, and a fancier steering wheel.
It was a cool car, but I sold it for money to finish another project.
340s were supposedly an option, but they were badged "Custom GT". However, Custom GT badges came on bucket seat cars.

340 was only offered on Swinger 340 in 1970

There was a limited run of 71 and 72 340 swingers made for two? dealers in Canada

Purple was one of the more populars color in 1970 on A, B, and E bodies.

You don’t see them now because they are 50 years old and the 318 and /6 cars were not collectible 20-30 years ago so they got scrapped. Whereas the Swinger 340’s people held onto.

They also made 1970 Dart GT 2-doors with 318 that was also a high trim level. Might have had similar or higher base price as a Custom.

For sporty models? Sure.

But regular ol' Mopars, not so much. For a V8 LH23, 3.2% of US-spec cars were FC7, which is approx 255.

My research showed the 340 and 383 where available in the 1969 Swingers and GTS models, the 383 weren't available in the GT models in 1969
They, 340 and 383, were, supposedly, available in the GT models in 1967 and Swingers and GT in1968

And your research would be wrong, Nothing larger than a 318 in ANY year Dart GT and nothing larger than a 340 in any year Swinger. The 67 was a GT with an "S" added and could only be a 383, the 67 GT largest engine is a 273 4-bbl...