Tiffany Haddish is down with doing a 'Blue Brothers' reboot with Cardi B ... if the money is right.

We got Tiff Friday at LAX and followed up on our convo last month with Dan Aykroyd, who told us about a script -- "Soul Sisters" -- that is sitting on numerous desks in Hollywood, just waiting for a studio to bite.

So now we followed up with Tiffany, who says she knows 'The Blues Bros' line and verse, and would sign a deal but she wants some serious $$$.

As for Cardi B as her co-star, Tiffany wisely concluded the time isn't exactly right for that, but when Cardi delivers her baby it's game on.