Well dwg will hold 3d surfaces but if Inventor is anything like Autocad you might have to tidy up the model a bit once you've imported it. Alternatively you could try exporting as 3DS file, the program below will convert 3ds for inventor.
The workflow issue you might have, and I'm guessing here, is that Inventor (if it's similar to Autocad) might be more suited to solid modelling data, not surfaces/faces like SU.
http://www.softpedia.com/get/Science-CAD/3DS-Import-for-Inventor.shtml
I'm not in any way an expert on file types though, I'm sure somebody here will give you some better advice.
I'm always up early, definately the best part of the day, but yes, I do have a deadline for tomorrow, not too pressurised though.