Gentlemen ... and ladies ... start your engines -- 'cause Richard Petty says he's ABSOLUTELY DOWN to race Danica Patrick in a 1-on-1 grudge match after trading shots in the media.

Of course, this whole thing started when Petty criticized Danica's crappy record -- and D.P.'s friend/team owner Tony Stewart said Petty and Patrick should settle their beef on the track.

Well, today ... Petty went on "Fox and Friends" and said HE ACCEPTS.

”Yeah you know, I’m 76 years old ... and it’s been 25 years since I’ve been in a racecar, but I’ll take that challenge.”

He then asked, "When's this gonna happen?"

Good question -- ball seems to be in Danica's court now.