I'm using the tension rod as the building lateral force resisting system. Other than A36 rod, are there any other higher strength rods that are widely available?
Stressproof 1144 ASTM A311 or Fatigueproof materials are commonly available however not in a threaded condition. DO NOT WELD either of these materials.
Brace rod would not normally be fully threaded. All you need is about 6" on each end. Check out ASTM A572 Grade 50 or F1554 Grade 55 S1 material. On the F1554 material you need to specify Supplementary Requirement 1 if you expect to be able to weld it.