French Montana Says Khloe's Ass Is the Best Endorsement for Nike 3D (VIDEO)

French Montana has an interesting theory ... this pic she posted on her website, khloewithak.com, could be a more powerful sales pitch for Nike than the company's potential new 3D printer.

We got French leaving Nice Guy in West Hollywood Wednesday when we asked whether Khloe Kardashian would be effective in pushing a proposed product, which would allow consumers to use a 3D printer to make shoes.

There's a lot of subtext ... French says his affection for his former GF is strong. But he's also embracing a product which is now the archrival of Adidas, the company that just hired new boyfriend James Harden as its pitchman.

Let's get real ... who notices the shoes?