Josh what Don said is very true, but if you shop around and watch ebay you'd be suprised at the bargains you can find. Until Paul gets here, what Don said about the aluminum manifolds and carb carb set ups is right on. Not only will it increase your performance but it will drop the weight of your engine by a lot! Aluminum water pumps will further drop the weight factor. If your looking for numbers, try Edelbrocks site. They make matched intake, cam and carb sets for this engine. I think Paul can also steer you in head modifications to get even more horsepower, but you probably won't need to go that route for 400 hp, I'm guessing it's just a combo of cam, intake, carb, and piston setup. Headers will help. Do you plan to rebuild it yourself or do you intend on sending it out to a shop? The reason I ask is I bought my long block rebuilt from a shop in Wa. that was cheaper than having it done locally. I also was able to get new parts like the intake and water pump off ebay for about 1/2 to 2/3rds what they were going for at any parts store. So hang in there, it's a good solid bullet proof engine when your done!