please help

The answer to how many locomotives are typically in a lash up varies as different considerations are met. If a train going across the flat prarie only needs 3 locomtives to move it quickly and efficiently, that same train then might need 8 to get it through mountain country. However here in Wyoming on the BNSF and UP, Locomotive lashups are typically 3 of modern 4400 hp units. (SD70Ms and Dash-9s) or 4 or 5 of older 3000 hp unis (SD40-2s C30-7s) As for if EMD and GE are MUed together. All the time around here. I have pictures of one consist where the Locomotive consists was A GE Dash-9. GE C30-7 EMD SD60 GE Dash 9 EMD GP50. In a typical lash up, the first locomotive faces foward and the last locomotive faces backwards. The locmotives in between can face any which way. I do know that for many years on the ATSF and it still might be the same on the BNSF that the policy was that the first and second locomotives always had to face foward so if the lead locomotive went down, the engine crew could swap locomotive posistions at the next passing siding. Finally the part of your question has a leading unit ever run backwards. The answer is kinda. For years the Norfolk and Western and the Southern Railway often ran their diesle locomotives with high short hoods in the back and the long hood foward into the late 1980s. This practice dates back to the very beginnings of diesledom when train crews were used to having a steam locomotive boiler in front of them. To better emulate this, diesle manufacturors placed the long hood of diesles at the front of the locomotive. When chopped nosed locos became popular in the late 1950s the long hood thus became the back end. So even though technicly Norfolk and Western and the Soutehrn weren't running backwards, with the modern generation of railfans used to the long hood being in the rear it very well could look like to them that they were indeed running that way.

I hope I have been able to help you.