[burnin oil]

I love 400sb Also. Be careful on the assembly though. They are the bastard motor of the small blocks. You need to make sure that the engine assembly is balanced correctly as they are the only one that are externally balanced. This means the balancer and flywheel need to go to the machine shop also for balancing. Once balanced these parts will not be able to be replaced without a rebalance of the rotating assembly! If you want to spend big money you can have it internally balanced like the rest of the small block family but it will take heavy metal, ie mallory being added to the crank. After this you can run a standard balancer and flywheel. If you run a stick shift this may be the best option. 400sb were always autos. This means the machine shop will not like you when it comes to balancing the flywheel. It takes alot of drilling to get it in balance. Been there!
A few other things to watch out for are the main bearings are a different size than a regular small block along with the oil pump drive rod. Also the rods are shorter. You can either reuse the stockers or switch to standard 5.7 rods as mentioned. I would let budget and piston selection guide this. The difference is only .05", 5.65" vs 5.7". I have yet to come across a steel crank for a 400. Spend the extra couple of dollars on a hyereutetic (sp) piston. Cracking a piston sucks! Get rings that match your pistons. I personally get chrome moly rings over the standard cast iron rings. Cheap upgrade.
Alot of guys on here really like the comp camshafts. From what I have been reading lately, both on this site and others, there has been alot of failures with them lately from whipping cam lobes. Alot of people blame the low zinc oils and this is a hot debate. Others are blaming the quality of the cam core and hardening process. I would personally look at another brand if only because of the failures in the last couple of years. Do your research on this and form your own judgement. I have a Lunati waiting for install in my motor.