I just saw this thread now and found alot of good info.
As for helmet preferences, I like full faced vs open.
Right now, I use a motorcycle helmet that is snell/DOT approved as I am only doing autox for now. Once my car is up again, I plan on getting a Simpson helmet. Also, IMO, if you have a fuel cell mounted in the trunk or somewhere inside the vehicle(not the OEM location) I'd recommend something that is fire retardent just in case....