At Chevrolet Motor Division, they're doing things by twos these days.

Chevy, not satisfied with introducing one new model, has introduced two -- the 1995 Chevrolet Lumina sedan and the 1995 Chevrolet Monte Carlo coupe.

Both cars are built on the same platform, and in standard form share the same fundamental mechanicals and basically the same dimensions. In essence, the Lumina is the four-door version of Chevy's new midsized offering and the Monte Carlo is the more sports oriented two-door version.

Monte Carlo production begins Monday in General Motors' Oshawa, Ontario, Canada, assembly plant. The Lumina begins production the week of March 7.

The appearance of the coupe will mark the return of a noted Chevrolet nameplate to the division's lineup of automobiles. The Monte Carlo first arrived in 1970, and was last produced as a 1988 model.

"It will be good for Chevrolet, and it will be good for us," said Bill Young, vice president of Dan Young Chevrolet. "I believe it will have an instant name recognition."

With the Monte Carlo being offered in a base LS series and an upscale Z34 version, Young said, "I feel the Z34 will be the best seller, because performance has a strong appeal to Monte Carlo drivers."

The overall dimensions of the two coupes are identical. But the Z34 with its performance orientation goes the high-tech dual overhead cam route in the engine department, as opposed to the more conventional push rod/rocker arm type motor in the LS.

With Chevy designing the sedan and coupe for different purposes, there are very minor differences in dimensional configurations.

The Lumina, which will be offered in base and LS series, is two-tenths of an inch longer in overall length, a difference so insignificant it's hardly worth noting. The four-door, however, is 1.4 inches higher than the coupe to provide a little more headroom for sedan users.

The Lumina, with its 60/40 front seat and fold-up arm rest, can accommodate six passengers. The Monte Carlo, in staying with its sports motif, is strictly a five-seater by virtue of its individual front seats being separated by a center console.

Technically, the fronts seats probably qualify as bucket seats. But unlike body-confining buckets found in many sports oriented automobiles, the seats in this Chevy are broad-based with moderate side bolsters for comfortable, non-fatigue-producing body support.

The sedans and the LS coupe are powered by Chevrolet's 3.1- liter (191 cubic inch) V-6, a tried and proven engine that by now must have been produced in the millions.

It's straightforward basic engineering that has been around since the time of Louis Chevrolet. There are two valves per cylinder actuated by a single camshaft mounted in the block, push rods and rocker arms, and the thing runs forever. Horsepower is 160, torque 185 foot-pounds, power that will give 3,400 pounds of automobile quite respectable performance.

For the performance devotees, Chevy is dropping a 3.4-liter (207 c ubic inch) V-6 into the Z34 that puts out 210 horsepower and 215 foot-pounds of torque. This engine packs four overhead cams and four valves per cylinder in the best speedway tradition.

For those needing four doors but still with the desire to go, it's optional in the Lumina LS.

The four-door is coming with two automatic transmission configurations, a less expensive three-speed and an electronically controlled four-speed that is GM's highly regarded 4T60 automatic.

The 4T60 will be standard equipment in the Lumina Z model and the only transmission offered in the Monte Carlo cars. While the three-speed automatic is less expensive, it doesn't quite fit the sporting image of Chevy's Monte Carlo.

Exteriors of both cars consist of flowing lines for minimum air turbulence, a design criteria that also contributes to minimum wind noise at speed. Interiors contain dual airbags, air, stereo and a plethora of power accessories and convenience items as standard.

The new cars r epresent a n important new direction for GM, and can be expected on the Indianapolis market in an April- May time frame.

"I'd like to see them cut into the (Ford) Taurus group," Young said. "And I have a feeling they will."

1995 Chevrolet Lumina and Monte Carlo Base price: Not available.Type: Front engine, front- wheel drive, six-passenger, midsized sedan (Lumina); five-passenger midsized coupe (Monte Carlo).Engine: 3.1 liters, OHV V-6, 12 valves, fuel injected, 160 horsepower, 185 foot-pounds of torque.Transmission: Three- speed automatic (base Lumina); four-speed automatic (Lumina LS/Monte Carlo).Mileage: Not available.Wheelbase: 107.5 inches.Length: 200.9 inches (Lumina); 200.7 inches (Monte Carlo).Width: 71.9 inches.Height: 55.2 inches (Lumina); 53.8 inches (Monte Carlo).Curb weight: 3,330 pounds (Lumina); 3,276 (Monte Carlo).Options: Premium AM/FM stereo, four-speed automatic transmission, anti-lock brakes, leather seating, premium fabric upholstery.