cat. converter Options

[6gcnoob]

my 94 celi was swapped with a 3sfe that i bought seized. i just bought the 5sfe to put back in. i was looking at it today, the 3sfe's cat. converter is bolted right up to the header followed by the down pipe. the 5sfe's header doesn't have a cat. converter, and for the state of CT, im pretty sure im going to need one for emissions as anyone else would. so what should i do here? by a cat, section off the down pipe under the car, and weld it in? i plan on buying a ebay header and later on do a custom exhaust, i go to a tech school and im in the auto body trade, so i am capable of welding. any suggestions would be appriciated.