Suggestions:
1. I would not choose a bolt (as my first choice) for a threaded device to receive the pressure that is going to be applied in this application. A couple of reasons for that. First the thread profile is not very strong for this purpose. A much better choice would be an ACME threaded ROD (5/8" x 10 ACME). Get it in 4140 Alloy Black Oxide and you'll have 125,000 psi tensile strength....or over 62 tons. ACME threads are very strong and not easily damaged. That why you see them on Vises, Ball Joint Tools, etc... Second, most longer bolts are not easily found in a grade higher than grade 8, sometimes 10.9 if you go metric. We want a safety factor here. ACME threaded ROD Is a good idea. I was looking at the threaded rod that came with ball joint press kit. But diameter large and rod to short. So found specialty bolt for my prototype on Friday of a long holiday weekend.
2. IF you choose/need to use a bolt....don't apply the pressure from the bolt head end. You'll essentially be trying to Ultra-Torque a bolt that has to then undergo Torsional Pressure 'twisting' as well as the Tensile Pressure (pulling in the axial direction). If you've ever tried to loosen a bolt from an object with a non-captured nut on the other end, then you know its easier to loosen the nut end first. (generally). Using a threaded rod allows you apply pressure more effectively and from either end (if needed). Good point. I had issue with my 3/4 break bar adapting down to 3/8", making to long to fit in between LCA on nut. I had though about reversing bolt, but just went at it as was set up. If anything, it did showcase how strong the ~11 grade is...LOL
Good suggestion.