I have 7 GMC's and no chev's but, it was quite common to put in a used engine that would fit when the old one went bad. Looks like someone converted from a speed on the column to a 4 speed which was also very common. Maybe the transmission came with the motor. Usually the the column shifter was removed, but they probably never got "a round tuit". Harrison was oem for GM radiators. Rochester carbs were also oem.
