Montgomery County Police Chief Charles A. Moose asked yesterday for the authority to appoint three assistant police chiefs, any or all of whom could be hired from outside the department.

Under the proposed legislation, submitted to the County Council yesterday by County Executive Douglas M. Duncan, the ranks of deputy chief and major would be abolished and replaced with three assistant chiefs who would oversee the department's three core divisions. Currently, the majors--who head the three divisions of training and staffing, investigation, and general administration--can come only from department ranks.

The proposal incorporates most of the changes that Moose announced last month when he said he planned to raise department heads from the rank of lieutenant to captain. It also would add a new planning unit, charged with drafting long-term growth for the 1,032-member department.

Montgomery County officials said yesterday they believe the proposal will have no trouble winning approval from the County Council.

The rank of deputy chief has been vacant since the August departure of Lt. Col. Thomas D. Evans, who had served as acting chief when Carol A. Mehrling resigned. Evans was passed over for the chief's position.

One of the three current majors has announced plans to leave at the end of February. Maj. Joseph R. Price, a 24-year member of the force who heads the department's training and staffing division, has agreed to lead the Leesburg police department.

Price, 48, who joined the force after graduating from the University of Scranton, headed several of the department's five districts and its police academy before being promoted to major.

Moose said in an interview yesterday that he had not set a timetable for appointing an interim or permanent replacement for Price. And though he said he planned to offer an assistant chief's job to the two remaining majors, Moose made clear he planned to look both inside and outside the department for a third assistant.

"It's always been my intent that [the three majors would] be the three assistant chiefs," Moose said yesterday. "There's a lot of talent in this organization, and I'd be remiss to not recognize that. But the doors are open."

CAPTION: Police Chief Charles A. Moose wants to abolish the ranks of deputy chief and major and replace them with three assistant chiefs.