This RWD-Swapped 1999 Pontiac Grand Prix Is a DIY GTO With a Five-Speed Manual

Pontiac's final rear-wheel-drive V8 coupe, the GTO, was never as popular as the classic it was named after. While brilliant by all accounts, it's now a rarity, and sometimes a pricey one at that. Fortunately, if you can't afford a GTO, you can apparently just make your own out of a Pontiac Grand Prix, and it costs less than half as much if you do it yourself.

This DIY GTO was constructed by Tyler Pitman, whom I last spoke to about his GM-built Chevy "Feretta" prototype with its unusual Isuzu V8. As the son of a master mechanic, Pitman learned how to modify on a budget by walking through junkyards and seeing what fit. A while back, he used this skill to build his first rear-drive Pontiac Grand Prix, which he described as "a complete mess." But he resolved to revisit the concept and do it better. Last December, when Pitman found a 1999 Grand Prix with a bad transmission for $500, he knew the time had come.

From having seen the underside of countless cars in his day, Pitman used visual memory to guess which parts might work. That began with the rear axle, whose suspension design made switching to another GM axle tricky. He figured out that a last-gen Ford Mustang (S550) would be relatively close, so he bought a rolled 2017 off Copart to pilfer its rear subframe, differential, and suspension. He adapted these using custom mounts and brackets for springs before reinforcing the rear floor and frame rails to make sure the Pontiac wouldn't crumple.

Moving forward, Pitman used a custom driveshaft to link to a five-speed Aisin AR-5 manual transmission from a Chevy Colorado. Using a clutch he bought off Amazon and a custom bell housing adapter, he affixed them to the 5.3-liter, all-aluminum V8 out of a 2009 Suburban. Cramming them all in required much more custom work, from fabricating a transmission tunnel to pushing the firewall back six inches and making mounts for all the new guts. The extra effort means the Pontiac's weight distribution is on point, though.

So is its ability to spin its tires, as the 5.3-liter Vortec was modded on the cheap. It has a hotter cam, eBay headers and a cheap turbo, plus a full three-inch exhaust. The fueling and intake are from an LS1, while the whole thing runs on a modified wiring harness and ECU from a 2008 Tahoe. Pitman tuned it himself, of course. (The radiator is a dual-row unit made for the Mazda Miata, and the aluminum oil pan is from Amazon, in case you wanted to know.)