Re: 67 or 68 camaro Power antenna, front fender?
If the area below the fender is anything like the 68-74 Nova's you will probably run into some barriers. The first is the side of the cowl goes pretty far outward towards the inside curvature of the fender and this will limit how close towards the windshield you can get. You will then be left with the area forward from the face of the firewall. The next obstruction may be the blower motor and housing. Forward of this under fender limitation would be the front inner fender housing. You may not be left with many possible locations.
Another option is to possibly have the hole on the fender be above the cowl side and then fabricate some type of notch or cavity to where the power antenna's motor and shaft are inside of the cowl side. You just have to see what kind of problems you may run into.
If I were to attempt this I would locate my hole in the topside of the fender and then put the fender on to then mark the topside of the cowl directly below this hole and then build a metal enclosure slightly bigger than the power antenna assembly and then after cutting a hole in the topside of the cowl, fully weld this enclosure to the cowl. To keep it frompossibly filling up with water I would weld in a drain tube nippleto where later I could add a small section of rubber tubing to it to direct and drain the water down and outside of the cowl.
I replied to a similiar question as yours back in 2006 but this guy didn't want to mess with his numbers matching car. I could see the reasoning but there never was a power antenna on his to start with so, who knows.
Years ago they used to make different styles of power antenna's like fully automatic, semi-automatic, motors fixed to the mast assembly and then also offered ones with remote motors but all required at least 8-14" of under fender clearance. Harada and Hirschmann brands are the ones to look at.
Jim