Header Gasket Problems!!!!!!!!!!hheellpp

I HAVE ANOTHER PROBLEM MY ENGINE IS A B16A SIRll
I BOUGHT A DC SPORTS HEADER AND ORDERED A HEADER GASKET FOR A 99-00 CIVIC SI I WAS TOLD SI AFTER MARKET PRODUCTS WILL ENTERCHANGE WITH AN SIRll MOTOR BUT WHEN BY GASKET CAME IN I TOOK MY HEADER UP WITH ME TO OREILYS AND THE GASKET DIDNT FIT ON THE HEADER BUTTT!!!! I MADE A CUTTOUT OF THE END OF THE HEADER WERE IT GOES TO THE BLOCK THEN LINED IT UP WITH MY FACTORY EXHAUST AND THE HOLES LINED UP JUST PERFECT ON TOP AND I THANK THEY LINED UP ON BOTTOM TOO
AFTER FINDING THAT OUT I CALLED THEM BACK AND TOLD THEM AND ALL THEY SAID IS THAT THEY ORDERED THE RITE GASKET AND IF THEY DID THEN WHY DO I HAVE A HEADER FOR A SI THAT WILL FIT ON AN SIRll BLOCK AND THE GASKET DOESNT
SHOULD I TRY SOMEONE ELSE OR DID I JUST GET LUCKY WITH THE WRONG HEADER
ALSO IS THERE ANY OTHER B-SERIES MOTOR PARTS THAAT WILL FIT ON MY MOTOR
I WOULD REALLY LIKE SOME HELP PLEASE!!!!!!!!!!!!!!!!

the bolt patterns are the same on all b series header (dont qoute me on the b20 though). the gaskets should also be interchangable.

i didnt really understand the post, because, my eyes were hurting from all the caps.