It is unclear. Parts-People sells two Bottom Base Metal Cover Assemblies for your laptop. I looked through those listings and in the Service Manual, but I cannot tell what the difference is. You may need to ask Parts-People. They usually respond to email within a day or so.
A component inside my cell XPS 9570 broke, first the gtx 1050ti stopped working and soon after, the laptop does not boot. I need to replace it. I live in Portugal so availability is not very good, Dell after warranty support is out of question, just shipping it to Germany for “analysis” is very expensive. I could find a motherboard replacement but it uses a different heat sink assembly (4 screws instead of 5) mine is 5. I can get another heat sink for 4 screws, but is that the only change in the motherboards? Will both (motherboard on new heatsink) fit in the same chassis , so if I buy the different motherboard and heatsink all is well? Can anyone confirm this? 
XPS 9570, motherboard replacement?