Jebby, take a piece of blank paper, and a pencil.
Hold the paper over the part of the frame you want to build the brackets for.
Take the pencil and rub it side ways over the frame section, all the way to the edges and across the Torx heads. Pull off the paper and you'll have a tracing of the exact size for the bracket, and where the bolts are. Just draw a cross hair on each copied bolt on your paper and you have a drilling template.
Lay it on your bracket and center punch your cross hairs to mark the brackets for drilling.
If memory serves me they are 8mm or 5/16" diameter on the threaded portion.
When in doubt just take one off and carry it into the store to match it up with what you want.
97 Sahara, 74 Renegade, 72 CJ5, 55 Willy's (the Beast) Boss 302, 6:34 gearing, Bose 901 speakers.
God I miss that Jeep. Forgot the kinda Jeep, 80 SX4.