How much? An engine like the one I linked to would typically run somewhere around $8k. If you really had the skill to do the assembly you might cut $500-1000 off that depending on what machine work you paid for.

Streetable? The more hp you want, especially in relation to "small" cubes, the more radical the cam, heads, ignition, and fuel need to be. If big horsepower is the goal over all else you start losing bottom end. In other words, it idles rough, won't accelerate smoothly until you're up to 25-3000 rpm, have poor vacuum, and so on. In day to day driving you're living at the wrong end of the engines "sweet" spot/range. That's why most people will recommend an engine that focuses more on torque, than hp. Torque will make for a happier street experience. That's why the strokers are so popular. They're better on torque than, for instance, a short stroke engine like the 327 is. That's not to say it's horrible, just less "torquey".

The mad man's suggestion is one way to deal with it. Build a nice performing street engine with some strong pistons and rods, and do the squeeze thing for that extra kick when needed. Just don't expect the engine to have a long life, especially if you get hooked on the button.