David Spade -- I'm Ridin' Dirty for Six Figures ... Scores Classic Movie Car

David Spade has gained a ton of muscle ... under the hood of the nearly million dollar '69 Dodge Daytona he just snagged.

David fell so hard for the model he drove in "Joe Dirt" and its upcoming sequel ... that he bid $900K on a sick fully-restored version of the Hemi-powered ride at Mecum Auctions last Friday.

The 426-hp copper-colored whip has had several other high profile owners ... like former NFL star Kevin Greene.

The real question: where's Spade gonna put the "Cowboy's Butts Drive Me Nuts!" bumper sticker?