Did the previous owner add it for structural and/or alignment reasons? I have nothing like this on my 6.0 NA. How much tension is in the cable? Enough to cause significant torque at the hull and cross beam joints? Torque translates to stress, not a good thing.
I am disappointed that an enginerd would not include a detailed freebody diagram wth all the important dimensions, forces and couples (we'll pass on material properties this time). Tsk Tsk. Your old statics prof would not be happy about this.