I do have a 78.
Maybe he's talking about a certificate of non-operation. It means the car is registered, but it's not allowed to be driven on the road. I don't think you're even allowed to park it on the road. It's used when a car will be off the road for a long period of time.
If you bring a car from out of state, you'll have to take it to a Department of Motor Vehicles. They will check the VINs and do the paperwork. You'll then have to go get a smog test, return, and provide proof of insurance to complete the registration.
If you bring a car from out of state and it's in a condition that can't be driven, you won't need a certificate of non-operation because you can't operate it. What you do then is begin the registration process, pay the fees and you're kind of hanging in limbo until it can be driven to have the VIN's checked out.
I went to a local place where I get my cars smogged and asked about the dual exhausts. He said it looked like I can do it, and that his book said the car has one catalytic converter. That's the same thing that was on the TA's with dual exhausts, so I should be ok. He also gave me the name of two good muffler shops to go talk to.