421 header ?
 

is it possible to put the header on without a cat or would this make it sound like s***?????i remember when i took the cat off my old car it made the exhaust sound like the baffles were busted, but the guy who put the exhaust on said it was due to the exhaust gasses not swirling properly....

Removing the cat would NOT be a good idea. The sound would be very loud and your car would be a polution hazzard. One car without a cat puts out as much emissions as 100 cars with a cat.

Go with a high flow cat, or keep the stock cat.