Aluminum vs. Steel Cross-shaft Question

[65Stang0_1]

I'm building some upper control arms for a '65 Mustang using 1" square material for the cross-shaft. I will drilling/tapping a bolt into each end of the cross-shaft for heim joints that allow the UCA to pivot. I have two (or three) questions:
1) If I use 7075-T6 aluminum w/a 83,000 tensile strength for the cross-shaft, will it be as strong or stronger as mild steel w/55,000 tensile strength? Which should I use for this application?

2) I'm using 3/4" x 5/8" heim joints for the above, should I use 5/8 bolt or a 1/2" with bushings? I'm leaning toward the 1/2" bolts due to 1" square that I'm tapping into.

Thanks for your help.

Vic