I have a friend in AZ who was pulled over for no seatbelt. The officer showed up and found the lap belt being used. No ticket, was legal in that officers eyes. (He used the lap belt when wheeling because the 3 point would lock up on him and he could not put it on when climbing into the truck when it is parked on a steep hill)
I have never seen a seatbelt law that states that it must be of any certain type. Just states that they must be worn when vehicle is in motion, usually just the front seat passengers.
If there is a law that states that only the OE seatbelt can be worn, then even the 3 point conversion are not legal. I can't see any problems with race type belts. If there is an issues, the cop has a thorn in him and you are getting the book thrown at you, the seatbelt issue would be the least of the worries.