nhigginson, it is possible and I have done it myself for my own use. I simply downloaded the version (V8 Factor Unleashed v1.2) from Xtremefactor and placed it in the appropriate folders in AMS. I haven't made a series file and just access threw 'all cars'. You may need to update veh files, can't remember if I had to do that.
Granted this process does not bring them to the quality of a proper conversion to AMS but it works none the less. Also added all the previous Dunlop Series and earlier season skin packs around for rfactor into AMS. Have some issues with some cars simply not showing up (e.g. Eggleston Motorsport cars) but had the same issue in GSCE and cannot for the life of me work out the reason and google doesn't offer any assistance.
So it is easily done but would be great if someone with skills I don't have would be able to do a proper conversion.