torsion bars

i have a 65 coronet and i am installing all new steering components. upper and lower ball joints, tie rods , pitman arm idler arm and all new bushings. i have to remove torsion bars to do bushings in lower control arm so while they are out i am wondering if i should replace them. but i dont know how to tell if they need replacing. the torsion bars are origanal and my car used to have a small block in it. now has a big block so i was thinking i should upgrade to bigger t-bars. is there anything i can check to see if they need to be replaced. or should i just replace them because they are 45 years old. hate to have one break going 70 mph

i have a 65 coronet and i am installing all new steering components. upper and lower ball joints, tie rods , pitman arm idler arm and all new bushings. i have to remove torsion bars to do bushings in lower control arm so while they are out i am wondering if i should replace them. but i dont know how to tell if they need replacing. the torsion bars are origanal and my car used to have a small block in it. now has a big block so i was thinking i should upgrade to bigger t-bars. is there anything i can check to see if they need to be replaced. or should i just replace them because they are 45 years old. hate to have one break going 70 mph