Hi,
when I put mine on I got a Glasstek one cause it has the reverse lip on the bottom like the steel factory one so you can use the slid on clips and bolts from the bottom up, if you look at the bracing on the bottom of the hood at the rear the factory has flat recesses in the braces, I used those for putting the rear holes in the hood and the scoop ended up being about a 1/2in from the rear of the hood. Also later when I put a small brace in the scoop opening in the center, when I drilled the hole there was and extra stiffner in my hood right in that spot, so I must have the scoop in the correct spot. I can take some close up pic's of the under side if you need them.
Russ