Buying all that stuff separately doesn't make sense, if you buy it altogether it's the same price:
Now, if you want to make it low pressure, I'm guessing this is what you need:
The orifice: http://www.agrisupply.com/orifice-for-asc/p/72051/
Regulator and hose: http://www.agrisupply.com/low-pressure-regulator-handwheel-pol-and-hose/p/36107/
A little cheaper than the high pressure application. You might need more components, don't know for sure as I'm a noob at this, just trying to figure it out so I can buy it as well.