 Differences from the PSU3A and 4A included the option of a ten-speed splitter gearbox with wide ratio five speed standard, a Worldmaster front axle and a Maudslay rear axle.From December 1970, shorter Leopards were altered to conform with the PSU5, resulting in a change to the B-suffix, these changes also applied to the last Panthers.Scottish Bus Group continued to take the manual-gearbox Leopard with O.600 engine until that was discontinued in 1972/3, the O.680 powered Leopards with the Leyland part-synchromesh gearbox were still coded PSU3.3R 

Late in 1974 spring-operated parking brakes, automatic brake adjusters, a water-cooled air compressor and a revised engine mounting resulted in a change to PSU3C, PSU4C and PSU5A.