Jerry Heasley January 4, 2018

Mark Thomure’s 1966 GT fastback might look like an old-school modified, but it’s not. He tore down the old school and waved bye-bye a long time ago. Crammed between shock towers, notched for clearance, is a crate 5.0L, 32-valve, dual overhead cam, all-aluminum V-8, packing 400-plus horsepower from the current Mustang GT lineup. How did Thomure fit this baby into a ’66 fastback and get all that power to the ground? He chose the Gateway 5.0L Coyote Installation Kit, which has everything Mark needed to swap out his 289, including suspension upgrades. Opening the hood at shows sets off myriad “hey come look at this” reactions.

Mark’s turnkey build sounds like an overnight success, which is possible if one just installs Gateway’s kit, but Thomure took a longer route. He started working on this car, in his words, “close to 30 years ago for a friend.” Thomure didn’t even own this fastback until 2000 when his friend decided to sell. “I drove the car until 2011, when it got totaled in a hail storm. That’s when I started installing the Gateway Performance suspension and getting it ready for the Coyote.”

Mark’s ’66 GT races with the big boys at club track events, like Mid-America last June at Hallett Motor Racing Circuit.

Today, Thomure does steel fabrication for a company in North County St. Louis, Missouri, but much of his adult life has been spent building Mustangs, including working for three different Mustang shops. He did not just write a check for the engine (which Gateway options in their installation kit) and suspension kit at once.

Fifty miles from his house in Warrenton, Missouri, is Gateway Classic Mustangs, which is the playground of Jason and Lonny Childress, the brothers we always see at the big Mustang events. This past June, Thomure parked his car with the Gateway Classic display at the Tulsa Mid-America Ford & Shelby meet. We were there and could see the connection. Thomure explained how he had helped some at Gateway and got the bug to modify his ’66 GT after a ride in the ’69 Boss 302 clone with a Coyote engine Jason and Lonny built on Hot Rod TV.

Mark Thomure has built a 1966 Mustang GT that he drives everywhere; to cruises, shows, track events, and occasionally for a trip to the grocery store. He went back with the original shade of Vintage Burgundy paint that this GT came with new. Mark said, “The spoiler was part of the front valance that I got from National Parts Depot. It’s a one-piece fiberglass unit that has a front valance and a chin spoiler all in one.

Thomure wanted to keep the original looks of his Vintage Burgundy ’66 Mustang, born in Dearborn as a GT with the A-code, 289-4V. He wasn’t about to modify the looks. His goal was to modify the car to handle and accelerate like a new Mustang GT with the looks of a classic Mustang GT. Thomure installed the suspension first, then later rounded up the dollars to purchase the Coyote engine, which is a part of Gateway’s kit. The other mods, such as the white Le Mans stripes, amount to personal preferences added over the years that give this Mustang an old-school modified appearance that serves to disguise the late-model GT get up and go.

Ford Racing decals alongside the Shelby stripes are a hint this Mustang might be more than old-school modified.

From the back, there is no indication rear wheel houses have been mini-tubbed.

In place of the 289 cubic inch display we see “5.0” on top of the “V” mounted on each front fender.

Ten spoke wheels from Vintage Wheel Works are 17x8 inches up front and mount P235/45/17 BFGoodrich G-Force Comp 2 tires.

You must open the hood and put this car on a lift to uncover the awesomeness that makes it drive more like a new Coyote-powered, late-model Mustang GT than the 289 four-barrel GT configuration in which this classic was born. The 5.0L Coyote is a tight fit, so the shock towers are notched. Mark used his own one-piece brace from each shock tower to the firewall. Gateway’s kit uses a two-bar system.

Inside, the standard interior has been upgraded to the Interior Décor Group “Pony interior”—seats, door panels, and woodgrain steering wheel. A long console accommodates a five-speed shifter for the T-5. The Rally Pac is vintage 1966. The fold-down rear seat is cool for cruising, as are rear speakers.

Mark Thomure’s smile comes from the thrill he gets nailing the throttle.