Notwithstanding subdivision (b) of Section 12804.9, class C also includes any two-axle motortruck or implement of husbandry weighing 4,000 pounds or more unladen when towing an implement of husbandry as specified in subdivision (n) of Section 36005, except that those vehicles shall not be operated in excess of 25 miles per hour on the highways and for not more than 25 miles on the highway from their point of origin.