Those bars were added to all big block cars and I believe any 4 speed car with 300hp small blocks....don't quote me on the latter.
As to the upper control arm modification....since you've already painted yours, I'd just radius the bottom rear inside corner per the picture I posted, the cut a 14 ga. wafer to the size I pictured, then drill the hold out to 3/4" (the wafer), and weld it 360* around the bolt hole and finish it out to 1/2+. You can take a 1/4" drill and simulate the spot weld depressions per the example I posted if you want to get picky....I would. Then paint again. No bending required, just adding a reinforcement "washer," wafer.
As to the upper control arm modification....since you've already painted yours, I'd just radius the bottom rear inside corner per the picture I posted, the cut a 14 ga. wafer to the size I pictured, then drill the hold out to 3/4" (the wafer), and weld it 360* around the bolt hole and finish it out to 1/2+. You can take a 1/4" drill and simulate the spot weld depressions per the example I posted if you want to get picky....I would. Then paint again. No bending required, just adding a reinforcement "washer," wafer.