It's not going to be easy. Get a section of pipe with the same inside diameter as the roll bar. Measure the distance from the trunk floor to the body, and cut the pipe 1-2" shorter than that. Now cut it in half length wise. By placing the pipe against the welded in stub, you can project the location of the stub up to the body. Dril 4-6 small holes up from the bottom in the correct circle pattern. Now use a jigsaw from the top to rough in the hole. Now use the support leg to grind out the hole to the correct specs.
If you overdo it, you'll have to fill it in with fiberglass. Wrap the roll bar in wax paper, and set it down on the stubs. Now you can fill in around the holes with the correct fiberglass repair material.
A good set of bezels will cover up a lot of mistakes.
I was happy to be within 3/8". It's not that critical. I used cardboard tubes on the lower mount points to allow me to position a pencil on the underside of the body.
I remember reading about someone using a LASER pointer to shoot a dot on the underbody.
If you plan on using trim rings just go for it. If you want a bare look, start small and trim as you fit the bars.
BTW, If you plan on a close fit make sure you have the body mounts all properly set i.e. the quick jacks, windshield, and doors fit with all the required shims at the lower body mount points. These things can change the final location of the roll bar holes.
The factory holes look great, round & even - but not in the correct location. The hole closest to the center of the car is at least 1/4" off. The body cutout option is worth more before you see the car; less after you realize it's not that hard to do and even less when you have to redo the factory work anyway.
Two suggestions. 1- The hooped roll bar leans backwards a few degrees so when you cut your holes be a wear of this. 2- For the down tube I did the same as boB did except I drilled one hole in the center of the circle. Threaded a string through the hole and taped one end to the roll bar receptor in the truck and taped the other end to the hooped roll bar. In doing it this way the string will give you the outside edge of the rollbar down tube. Hope this helps.
I drilled a small hole in the center of the hole that FFR marked on the body. Used a flaslight in the rollbar mount to make sure it looked good. Opened up the hole little by little using pvc pipe pieces to make sure I was still lined up. Worked great and didn't reall take that long.
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