I've used that location, a similar factory hole at a rear body panel gusset, and similar holes at the trunk latch support.
Worked fine in every case, whether a 512" Duster, various vintage race cars, early B bodies. My car in the avatar's been that way for over 30 years.
I also always add a heavy ground cable from block to chassis.
Fasten all ends as previously noted, and I like star washers to dig in.
On a unibody car, the chassis and parts welded to it become the "frame".
On something with a separate body/frame construction & isolators, I add ground cable frame/subframe to body.