AFAIK there's no such thing as a spitter for the header. You might be able to get PCI firewire card. Looking at the pictures though, while none of them appear to have shots looking into the internal port, the size/shape look suspiciously like a normal port, not a header+socket. I can't see any use for a port inside the case itself though.
![[H]ard|Forum](/styles/hardforum/xenforo/logo_dark.png){kind=logo}