An interchangeable concrete cutting chain-saw cutting assembly (500) adapted for installation upon a drive assembly (112) in exchange for a removed, different type cutting head assembly. The chainsaw cutting assembly (500) includes a housing (703) that has fasteners that releasably attach the housing (703) to a drive assembly (112) in an installed configuration. A ratio transmission (525) has a plurality of interconnected rotatable members (533, 535), each rotatable member (533, 535) having a mounting shaft (641, 643) positioned at a fixed location on the housing (703) by a bearing assembly (640, 642). The driven member (533) has a receiver that interconnects with a driveshaft (372) of the drive assembly (112) in the installed configuration whereby the driven member (533) is rotated by the drive assembly (112). The cutting chain drive member (535) operatively interconnected with a drive sprocket (707) whereby rotation of the cutting chain drive member (535) rotates the drive sprocket (707). The chainsaw cutting assembly (500) is pivotable relative to the drive assembly (112).