once you look at the hood-pins, you will see that its not that complicated to install them
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On the 7th Gen celica, there is already an indentation "circle" in the chassis of where the hood-pin drilling should be done at
Sorry I dont have a better photo, but it should be just outside the black "nubs" that are pictured here.
or an alternative to that would to just remove those "nubs" and use these holes... that would get your pins to be 100% symmetrical on either side
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I would suggest though, that you have this done by a professional bodyshop - since if you drill and make a mistake, it will cost a lot more money to fix that, then if it you were to just get it done professionally the first time around.
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but if you insist on installing them yourself...
1. Open hood
2. mark exact location for where you want your hoodpins located
3. drill holes in the metal frame of your car... to pass the hood pins through.
4. bolt hood pins into the holes you just drilled.
5. roughly set the height of the pins by looking at the neighboring light covers. Then tighten the pins!
7. dab some grease onto the tips of the pins. Let the hood down gently. The grease will mark the hood for drilling.
8. drill through the bottom layer of the hood. shape hole to fit with dremel.
9. Repeat the grease trick until everything is fit perfectly the way you want it.
10. drill through the top layer and shape with dremel
11. Once both layers are drilled and shaped properly. Set the height of the hood pins again.
12. position the top latch plate, mark and drill. Install w/ the small sheet-metal screws.
More detailed install here...
http://www.venommotorsports.com/library/hoodpins.asp