“Fast N’ Loud” host Richard Rawlings has found what he calls the car industry’s “Holy Grail” — the first two Pontiac Firebirds ever built.

Called simply “#1” and “#2,” the cars were manufactured by Pontiac engineers and were used as models for the 1967 Firebird, which revolutionized the world of sporty “muscle cars” when it rolled off the assembly line.

“We found the cars in a garage in Connecticut,” says Rawlings. “They were in a dilapidated barn and are the very first Firebirds . . . they were hand-made . . . and were used by GM to decide if they wanted to build the Firebird.”

Discovery will devote the April 21 and April 28 episodes of “Fast N’ Loud” to Rawlings’ find, showing how he and his crew, including Aaron Kaufman, restored both cars, which were purchased for a combined $65,000 and sold for $650,000 (after each car underwent $200,000 worth of restoration).

Rawlings says he learned about the Firebirds after selling a “pretty rare Corvette” to a client.

“I always have a habit of asking, ‘Do you have anything you want to sell?’ He told me he heard a story about a guy a couple of towns over who was supposed to have the [Firebirds],” he says. “A lot of times it turns out to be a ghost story — a ‘cool car’ turns out to be a four-door Nova.”

While these cars were the real deal — their authenticity was verified through scrupulous paperwork — they were in extremely bad shape.

“They were really beaten down and were rusted out, with their motors laying off to the side,” Rawlings says. “The [owner] was never going to restore them, so we made him a pretty hefty offer and the game was on.

“I wanted to sell them as they were … but somebody found out and word spread quickly before the cars even got back to Texas [where the show is based]. A guy wanted them fully restored to use as the centerpieces of a Pontiac museum in North Dakota, and he wanted them done in 60 days,” he says. “A full restoration for a regular shop would take a year or year-and-a-half, but we finished both cars in 60 days.

“To me, this is one of the biggest muscle-car finds in the last 20 years,” Rawlings says. “These cars were thought to have been long gone.”