I’ll open with I’m no expert on B bodies, but consider this;

ECS (Dave Walden) was about as meticulous as they come, his company offers only the “Magnum” version on his website.
https://ecsauto.com/products/air-cleaner-engine-identification-decal-1

PCG (Dave Patik) was also very detailed. He may offer a variation from factory but would state such on his site. He too offers only the “Magnum” version.
http://www.performancecargraphics.com/Small_Decals/Air_Cleaner_Lid/Checkerboard.htm

Spending some time performing various internet searches revealed little on the non Magnum version of the sticker, though I did see several on restored cars.

Is it possible that since the 340 Six Pack air cleaner decals are correct by the absence of the word “Magnum”, that someone assumed that the 440 was offered in the same configuration?

Will keep following this thread to see if anything supports the non magnum version

And finally, it’s sad that this site is so absent of the informed members of its past. I hear grumbling of the pop ups but wonder if it may be more the demise of the aging hobby, just as both Dave’s mentioned above have past