Planning on doing OMP, Puma, Adidas and Alpinestars in different designs too.
I used a few pieces from chargingcars helmet, mainly the Visor mount, the FIA logo and screws. Link: http://www.racedepartment.com/downloads/helmet-psd-template-4096hd.1331/ and provide the credit to him for a lot of the base of the helmet.
Once your suits/helmets are complete and converted to dds files, place the files in your car folder and make sure to delete the skin.ini from the same folder. (The skin.ini over rides the suits/helmets, this is why you must delete it)
Check out my Assetto Crew suit and Crew Helmet here on race department for an easier complete uniform.