Hi,
I'm afraid I have no easy answer to your question. The only thing I could think of would be:
1. Import the part you want to transfer from MS9 to MS8 into a Universal File.
2. The Universal File is in ASCII format, i.e. you can read or edit the file in a text editor (I recommend something like UltraEdit). Find the data entries that are specific to MS9 and edit them in a way that MS8 can read them.
3. Import the altered Universal File in MS8.
I'm afraid that this approach requires you to do a lot of editing, however, the Universal file format has not changed too much from MS8 to MS9 (at least not for FE entities!). Maybe you have to do only some minor alterations and end up with a perfectly readable part.
Cheers,
Daniel