Guns for cars, is it? Hmmm...
Well, for a Luger, it'd have to be something exotic, complex, and un-American. How about a Birdcage Maserati? Maybe that'd fit the Broomhandle Mauser better.
Fer the Ol' Colt SAA, it'd have to be something that's as American as it comes, simple and unstoppable. Therefore I nominate the Tin Lizzy.
S&W M-27/M-28 N-frame .357's are police cruisers like the Ford LTD Crown Victoria and the Chevy Caprice Classic.
Webley revolvers come in as Land Rovers.
Taurus Tracker .41 mag. Medium size, full power, off brand. 1970 AMC AMX with the 401, well-known to be tough to beat.
Magnum Research Big Friggin' Revolver in .45-70. Make it bigger, and if it sticks out, chrome it. Harley-Davidson.
Astra 400/600's are full-power BLOWBACK service guns. Ugly, powerful, and agriculturally simple. AMC Gremlin. (You can get Gremlins with V-8's. 401's a bolt-in. Stand back.)
S&W M-19. Medium size, extra oomph. Ford Mustang Boss 302.
H&K P7. Euro-wierd, but very slick. Porsche 944S Turbo.
S&W M&P/M-10 and related plain vanilla .38's. Chevy Nova/Dodge Duster with the Stovebolt/Slant Six.
Rogak P-18, the bastard Steyr GB in stainless. A Delorian, I think.
All Ruger revolvers are trucks. Probably military trucks. Maybe half-tracks. With one exception.
The Ruger SRH in .454 Casull is a Hemi 'Cuda.
S&W Triple Locks are refined, obsolete elegance. Therefore a 1947 Buick Super Estate Wagon, typifying post-war elegance. I NEED one of these in the worst way:
Fun thread!