While 9900-9903 were power cars with RPO and baggage compartments, only one more, the unique 9908, was built. 9904-9907 were locomotives with the twin 900 hp 12-cylinder engine layout that GM-EMC's early E-units would use. 9906 and 9907, built for the ten car "Denver Zephyr" sets in 1936, included booster units. 9908 used the new 1000 hp GM 567 engine in a single engine configuration. After 9908, all of Burlington's new passenger locomotives were standard production models, with the cosmetic stainless steel bodywork of the E5s their only custom feature.