Disclaimer first: I went through this a couple years ago and things may have changed....
Without SB100 Car is registered as year you start DMV process. Smog requirements are those in effect for year of block. Smog check is required every two years.
With SB100 Car is registered as year you start DMV process. Smog check is done ONE time only during reg process and is not required again. Duning that inspection much attention was paid to my PCV routing (late 60's FE), but NO attention was paid to what the emmissions actally were....
Yes, you don't NEED the SB100, but you don't really NEED that 427 either.......
-Jon