My vote goes to the 400
Years ago I built or was involved in building several SBC�s (305s, 327s, 350s, 383s, 400) only one of them was a 400 which was the last and best, the 400 was built after researching and putting aside the bad reputation it had.
Now 20 years later I am back to building another SBC, I did my research and choose to build another 400, more bang for the buck.
The issues the 400 have are basic and very easy to over come (keep in mind the 383 also has it�s unique issues). 1) It is a SBC with a 4.125 bore so you are limited to how far you can bore it out, 2) It is a bigger displacement motor and creates more HP and heat, it will need a bigger radiator, 3) The design of the block (so we can have more cubic inches) requires steam holes, so use the correct head gasket with steam holes and drill the steam holes in the heads.
Take care of these issues and a 406 will run just as well as a 383, but when you stomp the gas pedal you will feel the extra cubic inches the 406 has.
400 Pro�s
No if and or buts there is NO replacement for displacement:
350, .30 over, 3.75 stroke = 383 CI.
400, .30 over, 3.75 stroke = 406 CI.
It cost about the same to build a 406 or 383.
You can put a slightly bigger cam (more HP and Torque) in the 400 and maintain a good idle.
400 Con�s
The 400 blocks are getting hard to come by, but they are out there.
Weak main webbing, this is not a problem unless you are building a wild racing motor.
DISCLAIMER: I am no expert my statements are based on my personal research and experiences, I have NO problem with some one giving constructive criticism, I don�t mind learning even if I�m wrong, so lets hear it.
Both the 383 and 406 are awesome motors and almost anyone is going to be happy with ether one, if you have a 350 block sitting in your garage build a 383, if you have a 400 block build a 406, it�s that simple.
406chevelle