In 1904, Cadillac offered two models. The Model A was a continuation of the 1903. It had a delivery body with detachable top. Horsepower increased to 8.25. Clincher tires became standard equipment. An optional 60 inch tread was available. A pressure fed multiple oiler was introduced.

The Model B was the same as the Model A except the chassis had a pressed steel frame and axles. It featured front axle girder style (which was not available in the wide tread option) and single transverse half-elliptic front spring. Cranking (counterclockwise) was only on the left side; but a decompression device was provided to facilitate cranking. A safety device was introduced to prevent the crank from being inserted when the spark control lever was in the advanced position. Horsepower rating increased to 8.25; but this was more an issue of confidence in the engine rather than any engine design changes.

The body of the Model B was an inverted box rather than the sloping, curved dash. The radiator was vertical and below frame instead of the front mounted sloping unit on the Model A. A joint in body at dash allowed the body to be slid off without lifting. A surrey body style was added with a side entrance detachable tonneau. The delivery top was no longer detachable. The weight of all body styles was reduced by as much as 70 pounds. Prices increased $50. When the street was muddy, cars with rear entrance tonneau were backed in perpendicular to the sidewalk so passengers did not have to walk in the mud. The side entrance surrey ended this inconvenience.

Once again serial numbers were not used for Model A or B. The engine numbers were stamped two places on crankcase: top, right edge of cylinder flange, near the water outlet; and right, front face, just below top cover. The blank spaces on patent plate was for additional patent dates, not engine number. Model A engine numbers ranged from 3500 to 4018. Model B numbers were 2500 to 3500.