400hp shouldn't require anything too fancy. For an intake, a Performer RPM Air Gap should do fine. Run 9.5-10.5:1 compression, Vortec heads modified for higher lift springs and screw in studs, Comp XE268 cam, HEI style distributor ( Get one from MSD, it really isn't that much more than a modified stock junkyard distributor when all is said and done), a properly set up Quadrajet will be much better on the street than most aftermarket carbs and can support 400hp, and a set of 1 5/8 or 1 3/4 primary headers with a good 2 1/2 in dual exhaust system or a 3.5 in single.
I run a similar combo in my 355 and the computer sim says it makes 350hp with a milder cam and a standard Performer intake. I have also found similar engines and their dyno sheets on the internet to corroborate the sim. However, that is irrelevant to the 400 ft lbs of torque it makes from just over 2,000 to around 5,000 rpm! If you have the choice between two cams, always opt for the smaller one in a street car. Big cams are not a lot of fun in rush hour traffic or on crowded city streets. ( I love my XE262 BTW). HP may look sexier on paper, but in a heavy G body, torque will win the day. Remember that horsepower is a mathematically derived figure based on rpm and torque and not an actual measured output. Given enough RPM, an engine making 2 ft lb of torque can mathematically make 400hp. (IIRC, HP=(torque*RPM)/5252) Go for the biggest area under the torque curve and disregard your peak numbers as they are irrelevant. 400hp at 7500RPM means nothing in a car that is driven mostly below 3,000 rpm. A Honda S2000 has a power peak around 7500RPM, (and a redline of around 9,000 RPM in the original 2 liter version!!!) but is a complete dog to drive. Sure it makes more hp than a stock 5.0 Mustang, but the power curve is so damn peaky that it is actually slower than the Mustang in a drag race. All that RPM may be fun to wind out, but it doesn't necessarily make it faster.
While I am on my high horse, I'll say something about Edelbrock too. Edelbrock products are some of the nicest on the market and very well engineered. Sure they are not the cheapest, but they are packaged with pretty good instructions, and usually include all necessary hardware that is not re-used from the old parts. Compared to a lot of other companies they usually have their sh*t together. I got the upper arms for the
B body spindles for my Cutlass form Global West, for example. The instructions were a photocopied sheet of paper with poor grammar, punctuation and loads of misspellings. It was like it was written hastily by a 4th grader. When I got a set of Edelbrock headers however, the instructions were pretty well written, they included even the most minor of items like good gaskets, bolt spacers for the accessories to make up for the flange thickness of the cast manifolds, a O2 sensor wire extender, etc. Just remember that the cheaper part is not all that cheap if it means you have to go out and buy things that should have been included. Nor is it cheap if it breaks due to poor quality.
