Your car may just not be programmed in to the database as being a "fit". I
believe any B-body small block headers will fit.
Having said that, I will state what I have said before on some other threads. Many small block B-body headers route three driver side tubes under the steering. This makes the headers hang down really low and virtually guarantees that you will smash them into oblivion. (Ask me how I know
)
All the "offending" headers look very similar. Look at the headers below. The driver side has three tubes that go straight down, and then make a 90* turn towards the back. Lots of manufacturers have them, so I won't give you the name of these - it doesn't matter and I am not trying to bash (pun intended) any particular manufacturer.
View attachment 1588617
Bottom line is stay away from any headers that look like this if you need ground clearance to drive your car on regular roads.