Technically there are only 3 different species of Pituophis and they don't line up with bull, pine or gopher.
Who ever told you that west coast east coast thing was wrong. They are different sub-species not localities. They are genetically and morphological distinct. The east coast is mostly pines not gophers. The west coast is mostly gophers and the middle of the country is a mix with bulls being there. This is very arbitrary and I am not saying that gophers only occur on the west coast and pines in the east. Bulls go all the way up the center of the country to Canada.
Gophers are different than bulls big time!
They all have a lot of localities but make sure you buy from a reputable breeder for those.