The Class 387 is a variant of the electrostar that has extra 650hp over the class 375 and 377. These trains also have a top speed 10mph faster than the 375s and 377s. While a slightly adapted model of the 375 or 377 would work, they would need some adjustments to their performance to reflect the differences between the electrostars already in game and the Class 387. Minor adjustments to the cab should also be made, to reflect any differences between the existing electrostars and the class 387. As far as liveries are concerned, Thameslink and Gatwick Express would be the best to include in a Class 387 pack, along with scenarios for the London - Bedford and London - Brighton routes. Thameslink Gatwick Express Both pictures from Wikipedia While I am aware of the existence of these as liveries for the existing electrostar models, they do not have the improvements to power and speed that were made to the class 387, with the speedometer still showing the 100mph limit instead of the 387s 110mph limit. This is why I believe that it would be better to have a dedicated model for the 387 than just relying on using a repaint of the 375s/377s. Feel free to discuss in the comments.