Dumb Question, but please help

Ok, sorry guys, I know that this could be in the wrong forum all together, but I desperately need help, as my car is already taken apart. Anyways, I have a DC Sports shorty header, a Megan Racing cat-back, and Megan racing high flow cat with down pipe, all are going on a 2003 Honda Civic ex coupe (D17). Problem is-cat-back and cat bolt up great, but the header is not going on, doesnt fit well with the cat at all. I dont know if i need anything else or not, but I need help!!! THANKS

You may need a different flange for it to fit right or maybe weld it together.

put the exhaust and cat into the trunk or back of the car, install the header, drive to a local exhaust shop and have the rest installed. make sure that they only change the indexing of the flange, not just weld the exhaust up. exhaust shops are bad about hacking the flanges off and just welding it up, then you have one solid exhaust from the head to the tail of the car. that is bad. good luck.