Why the focus on "400" horsepower?

Its just a number.

There are soooo many things to consider; that's why you're hearing $500 to $5,000.

It all depends on what YOU want to do with the vehicle; not just that you want "400" horsepower.

The whole thing has to be a plan; you have to match cam, intake, carb, stall converter, gear ratio, and tire size all to what you want out of the vehicles purpose.

Is fuel mileage important? Is high rpm important? Is 75 mph for freeway driving important?

So my point is there are many things you can do to a vehicle to make it perform and FEEL more powerful and like it has more horsepower, without really adding horsepower IN the engine. You shouldn't focus on wanting "400" horsepower as much as doing the things to make it perform "better" - for whatever it is you're looking for.

Change your gear ratio.
Add an intake manifold and carb.
Add headers.
Add a bigger cam.
Change heads.

If you want to change compression more than what you can do with heads and thin head gaskets, thats when your money will be falling out of your pocket. Like the poster above said "$3500 and you assemble." And why I said, "$5,000." Getting into an engine for a complete rebuild isn't cheap.

I'm just offering some advice and points for you to think about. I'm not critiquing or judging you or anyone else's comments, just trying to help.