Before I did my SBC swap on my 84 CJ I went to the state motor dept and asked about smog requirements. I was in Illinois at that time and was told that I must have proof of the year of the engine (1972) and must leave all and any exhaust components that were factory installed on my 84 CJ (single exhaust and cat).
When I go for the yearly emissions tests I must have all my proof of engine year and they would test the emission requirements for a 1972, 350 chevy.
This was a big pain in the A$$. The state would not allow me dual exhaust because my 1984 only had single. So I made up a "Y" pipe to connect my stock headers to my cat and single exhaust system. I would go to the testing lanes sometimes I would pass and sometimes I would fail and they would give me a waiver sticker.
I then would go home, remove the exhaust system, put my headers and flow masters back on and run for a year until I needed to test again.
I did this for about 8 years until I moved to a state that didnt have emissions testing.
I am not sure what your state requirements are for emissions but you may want to check it out before you swap and throw away some parts that you might need latter.
Good luck with the swap.
You will like it