I'm not sure but I know the Regal is the same body style as a Chevy Lumina. And the low side fitting was under the air filter on the accumulator. If nothing else the low side lines are the bigger lines that run from the condensor in front of the radiator to the evaporator core in the air box by the fire wall and out to the accumulator back to the compressor. Just follow the lines until you find it. You may need to remove some parts to get at it or you may have to go under the car to get at it also.
