Delta codeshare on VS flights

Hi

Have noticed that you can now book VS flights through delta on their codeshare. Does anyone know if you can request extra leg room or emergency exit seats in advance like you can with Virgin direct?

If so who would you call, VS or Delta.

Currently flight prices on Delta are £50 less than the same VS flight.

In my humble opinion I would say call the airline you are looking to book through and see what's what. In this case DL
If the answer isn't satisfactory then VS and pay the extra if it means you can get the extra leg room seats.