When I installed mine, I installed nut serts into the roof for the hinge screws. I didn't want sheet metal screws holding my original louvers on the car.
I just set mine in place and once positioned, I marked the location of the hinge holes by placing masking tape on the roof and then used a marker to mark the hole locations on the tape. After drilling the holes, I then used a nutsert tool to install the threaded nutserts. After installing the louvers, I then located the lower pins using a similar procedure. Be sure and use sealant at the upper screws and lower pins (hood pins).