We have had this discussion before about big block vs small block, here is the link
http://chevelleforum.org/showthread....highlight=Dart
Now for me, I originally started out with a 350 small block and we built the motor, only to find out that there was a problem with the block. My husband, grumpy, had worked with DART to build the top of the motor. So it was obvious to go with a DART block. We ended up getting a DART 400 short block. After a few problems we ended up with 523 hp @ 5900 rpm. I love this motor, it sounds good, runs great and has lots of power. Here is a link to what I have in the motor.
http://chevelleforum.org/showthread....highlight=Dart
Good Luck on your decision.