The majority of making a snorkel is a no-brainer, mostly a matter of style, which everyone has their own.  The main problem I had was a streamlined, good-looking way of attaching the thing to the intake.  Well, I got an old oilbath canister from Scott Ingham and cut off the part that attaches on the inside of the intake louver.  Fits like it was made for it because it was.  Ultimately, it cost about 120-150 in materials and time.
I used 2.5 inch mandrel bent pipe from Jegs.  One thing to keep in mind is when you're flaring the pipe to fit your upright,
take the pipe with you so you can get a tight fit but leave enough wiggle room to adjust the fit when it's on the truck.