When General Motors boycotted all forms of racing for its divisions, Sox and Martin reluctantly signed on with rival Mercury Division. The former Chevy racers were provided with one of the new '64 Comets equipped with a dual four-barrel, 427 FE Series V-8, with a fiberglass front end, a heavy-duty Top Loader four-speed transmission, and a heavy-duty 9-inch Ford rear axle. Their car was a Comet hardtop coupe, while Mercury teammate Don Nicholson chose the Comet station wagon for its better rear weight distribution. The difference between coupe and wagon was insignificant, and they found immediate success running A/Factory Experimental class in open competition and match races against all challengers in the southeast. They were mostly unknown by the California guys, but their Mercury Division sponsors ordered its North Carolina-based S&M race team to report to Pomona, California, to race at the NHRA Winternationals.

Uncharacteristically, Ronnie was late off the line and lost the A/FX class trophy to Bill Shrewsberry, who later gained fame as a driver of the Hurst Hemi Under Glass Barracuda and other exhibition wheelstanders. Stung by the loss, he righted the ship in that Sunday's Top Stock final eliminations, cleaning house and winning the posted cash ($500), as well as a new Dodge 426 Hemi engine. In those days before huge factory funding, it was usually difficult to make ends meet, so they promptly sold the Hemi engine to help pay for their trip back home to North Carolina.

It was the beginning of a very successful year for the Sox & Martin team and Mercury, and offered what seemed like an exciting proposal for the duo's '65 racing campaign. However, a contract dispute with Mercury found S&M abandoning their short-lived association with Mercury. instead, they signed with Chrysler's Plymouth Division after they were convinced the impressive 426 Hemi engines would be theirs. The team took delivery of their '65 Plymouth Belvedere 426 Hemi four-speed sedan and launched the Plymouth Division's second most successful racing team, just behind NASCAR's Richard Petty.

The familiar red, white, and blue Sox & Martin colors adorned the '65 legal Super Stocker, but the altered wheelbase '65 Plymouth A/FX was easily the most popular with fans. Sox & Martin ran this gutted, lightweight, steel-bodied, homebuilt Funny Car in AHRA open competition events and match races at both well-known and two-lane blacktop-style backwoods local drag strips. They easily racked up an impressive win record against the best match race rivals of the day. Burning through powdered rosin and then backing up to do several more similar burn-throughs for the crowd, the S&M team wowed the usually capacity crowds, running low 9-second runs at 140-plus mph. Those wide-open throttle, power-shifted runs were often performed with the front wheels off the pavement as the legend of Mr. Four Speed grew.

The AWB '65 led to an even wilder '66 Plymouth built on the all-new Barracuda platform. Sox & Martin gutted the car, added structural strength with a tube steel rollcage, added a lightweight fiberglass front clip, altered the wheelbase by shifting the body to the rear on the chassis, and dropped in one of Jake King's powerful 426 Hemi engines. The traditional S&M paint was complemented by eight 26-inch-long ram tubes atop a Hilborn fuel injector that made the crowd's eyes water with heavy doses of nitromethane and alcohol racing fuel. Big loads of nitro and stroker crank match race engines were known to create excessive shock loading on the drivetrain parts and reliability suffered. To remedy the new Funny Car's hunger for parts, S&M reluctantly added a modified Torqueflite transmission. Although Ronnie missed the four-speed, the auto transmission's softer launches all but eliminated the Hemi's hunger for parts.