Ok, this is a fun project. Its very time consuming, but I think will turn out really well.
First you have to make a foam plug to get your shape. I chose to use insulation sheets from Sutherlands. Anyway, cut about 4 or 5 5" inch strips and glue them together with a hot glue glue:
Then you just begin to shape your block to the shape you want your snorkel to look like in the end. I recommend that you go about .75 of an inch smaller in diameter than you want because you are going to be adding fiberglass and bondo later in the process:
Keep shaping until you get the right look, then make your upper piece. Once you get everything looking good wrap it with tape. Painters tape would be better if you have it handy. Make sure you make the indentions for your mounting brackets and to clear the hood and the antenna:
Now go tape off the section around your air box in preparation for a fiberglass mold:
Wrap your plug with fiberglass chop mat. I used small staples to hold the chop mat in place. I would NOT recommend that as they did not come apart like I planned later in the process...grrr.
Lay mat around your air box. Oh...I forgot to mention before you lay any mat give your tape a good once over with Johnsons floor paste wax. This will allow the setup fiberglass to release easily: