Todd Bodine won the Ford 200, but all eyes were on the championship contenders as Hornaday tried desperately to make up ground after falling behind in the pits during the final caution at Homestead-Miami Speedway.
Benson, who came into the race with a three-point lead, finished seventh, one position ahead of Hornaday after the dramatic green-white-checker finish.
"Tonight was tough," Benson said. "Tonight was about (crew chief) Trip Bruce and making the calls he did. ... Trip said early on we might not be the fastest, but it was going to be the smartest one that won it. And that's what it came down to -- Trip's calls."
Bruce said it was obvious Hornaday had a better truck most of the night.
"They made a mistake," the crew chief said. "I think they would have beat us if they stayed out. But we ran hard to the end and it's our championship."
Hornaday led early in the race, with Benson falling several positions behind. But Bruce's decision to put only two tires on Benson's Toyota truck during a caution on lap 92 of the event scheduled to go 134 laps vaulted Benson from ninth to his first lead of the night.
He and Hornaday swapped positions several times until Mike Skinner's shredded tire brought out another yellow flag on lap 125. During the ensuing caution period, runaway leader Kyle Busch pitted and Hornaday's crew chief Rick Ren brought his driver's Chevrolet onto pit road for a four-tire stop, while Bruce kept Benson on the track.
When the race was restarted, Benson was sixth and Hornaday 13th. It appeared three-time and defending truck champion Hornaday would catch Benson, but rookie Tayler Malsam crashed on lap 132, forcing a two-lap overtime. Hornaday ran out of time.
"I was frustrated," Hornaday said of the four-tire stop. "My radio wouldn't work. I didn't want to stop. My truck was good enough to stay out, but they kept telling me to come in and I had no choice. Then it hurt me that a lot of those guys only took two tires.
"It was a good call, but it didn't work. I ran out of laps."
Benson still looked a little surprised to be the champion after celebrating in Victory Circle.
"I was kind of crying down the backstretch but, hopefully, I'm over it," he said. "My wife kept telling me that I only had to win by one. ... That was my approach going into the race."
It took NASCAR several minutes to determine that Benson, the 1995 Nationwide -- then Busch -- Series champion, won this title.
"I'm just so happy for (truck owners) Bill and Gail Davis," said Benson, who will not return to the team next season. "It took them a long time for them to tell me who actually won it, but I'm pretty happy now. This means a lot."
Sprint Cup star Busch built a lead of more than 5 seconds midway through the race, fell back after a pit stop and retook the lead before pitting again during the late caution.
It appeared he might get to the front again, but the last caution flag slowed him down and he wound up fourth as Bodine passed rookie Brian Scott for the win and Kevin Harvick, Hornaday's truck owner, finished third.
A year ago, Hornaday overcame Skinner's 29-point lead in the final race to win his third title when the leader got caught up in a crash. This time, the longtime NASCAR star fell just short.
"Ron's truck was really good, but it came down to pit strategy at the end and that's the way it goes," the disappointed Harvick said. "But I think everybody is happy for Johnny. He's been so close before."
Bodine, a former series champion, was surprised to find himself in Victory Circle after making a late-race pass on rookie Brian Scott to take the lead.
"We had a troublesome race truck," Bodine said. "They got us a lot of spots on pit road. The fastest truck doesn't always win, and that's the way ti was tonight.
"If those other guys hadn't pitted, we'd have probably run no better than second."
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