I have a question about the USDM ITR header. This guy is going to sell me his b18c1 swap and it has a USDM ITR header. i'll be putting this swap into my 2000 civic ex coupe. what exhaust modification will i need to make in order for this header to fit? will i need to add some piping? how large is the opening?

my current setup is 2000 civic ex coupe with stock cat conv and apexi n1 full catback.

thanks!