To give some ideas regard early diesel and electric engines, here´s a timeline of some alternate engines that could be built:
1915: New York Central introduce the Pullman Motor L-1 Class, built by GE and Pullman, these motor cars have 3-rail catch and a diesel motor, make one of first dual-power engines to be built;
1923: Baldwin introduce the model know as DP-X1-2000 (Diesel Prototype, one of type, 2,000 hp). Despite of initial ideas to be a mainline design, but not be so very weel, they became good transfer and yard operations engine. B&O in 1925 bought the prototype unit, and ask to Baldwin to built more 4 units.
1933: ALCO introduce the Type I prototype articulated diesel-electric locomotive. The model have a relative sucess at the time, as roads off Southern Pacific, Lackwanna, Great Northern, New York Central and Union Pacific order at total of 40 units between 1936 - 1938, and give ALCO a advantage on diesel market over GE and EMD. The Type I have dual cabs and 1,500 hp, and make a base for latter models as ALCO DL-202, FA-1 and PA ones.
1936: PRR make a proposal to ALCO for the built of a center-cab diesel power. This make the ALCO DL-101 as 14 units are built for massive freights and use the same streamliner design that electric GG-1. On Classification System, them DL-101 became ARS-15 (ALCO Road Switcher 1,500 hp).
1937: Works are make on General Electric streamliner DMU, know as "The Liberty". Consist of two power cars, two first class, three second class and one restaurant. It´s have a 2.400hp and a top speed of 180 kph.
1947: ALCO introduce the DL-202, know as "Black Maria" they prototype unit. The model pass to be used by Delaware & Hudson, Boston & Maine, New York Central and Seaboard.
1948: The higher speed ALCO-GE common built DMU Dieseliner 30, or DSL-30, are introduce and became one of most famous and used trainsets. Some units are used until 70s during Amtrak HSR-era.
1951: As for renew of passenger service, Pullman introduce the Superliner-I DMU, consist of 10 coaches. (OTL New Haven Comet design but non-articulated and more cars)
- ALCO introduce the road freight unit DL-36, in a Loewy-inspired design if 3,600 hp, bought by Burlington, Northern Pacific, Baltimore & Ohio and Florida East Coast.
1952: Milwaukee Road GE-built Olimpia double-deck EMU are introduce on Chicago - Milwaukee route as a fast intercity service.
1955: To compete if ALCO and EMD for US motive power, as well the necessity to introduce a newly fast train to new high speed routes built during 50s, GE design the Americaliner Diesel Xpress DXP-55, a trainset consist of two power cars and 8 coaches between, as express service consist.