The base plate for every car is different. Not sure what car this equipment came from....are you?
Changing your choice from a dolly to flat towing is based on what vehicle you are looking to tow. Not all vehicles can be flat towed. Manual transmission vehicles will give you a slightly wider selection but there are still limitations. Read the owners manual for specific details about whether the vehicle in mind CAN be towed or not............usually under the heading of "Recreational Towing".
This link may help
What Cars Can Be Flat-Towed Behind an RV? on Edmunds.com
__________________
Ken and Terry
2018 Sunseeker 2430S-CD, nicely modified and carried by a 2017 Ford E450 Sport
Former Georgetown 330TS owner for 10 years with more mods than I can count, pushed by our 2017 GMC Terrain