Conrad, best known for his roles in "Baa Baa Black Sheep" and "The Wild Wild West," was arrested on suspicion of driving under the influence of alcohol after the March 31 crash on Highway 4 near Arnold.
Police wouldn't release details of Conrad's blood-alcohol test, but said Monday the results will warrant the felony charge of driving under the influence with injury to another person.
Conrad was taken by helicopter to a Modesto hospital, about 60 miles southwest of the accident. Donna Gaba, who works for Conrad's agent, David Shapira, said at the time the actor was in stable condition. A call to the agent's office wasn't immediately returned.
The driver of the other vehicle, 26-year-old Kevin Burnett of Forest Meadows, suffered multiple injuries, Officer Bryan Duquesnel said Monday.
"He (Conrad) caused significant injury to Mr. Burnett and his blood alcohol results place us in a position that we're going to recommend to the district attorney's office that he face a felony charge," Duquesnel said.
Duquesnel said the recommendation to file charges would be forwarded within a week to the Calaveras County district attorney's office.
Police listed Conrad's age at 74. Television and film reference guides report the actor is 68.