Yes, and let me see if I can make a mountain out of a geosyncline.
I presume you don't mean to add a tube shock mount to the existing friction shock arm as it would only pivot with the arm rather than compress the shock...... Occasioinally, I am able to grasp the obvious.
You can remove the friction shocks and weld a vertical plate/bracket to the end of the crossmember tube. I would then add a tube or plate to the back of the shock mounting bracket to form a triangle using as it's three sides, the shcck mount bracket, the crossmember tube and this third added piece. Did I say that right?
Alternatively, you can mount these same two (per side) braclets to the x-member tube just inboard of the friction shock to retain the friction shock.
I would not connect the lower end of the shock to the existing mount on the axle, although you could. I would mount the lower end of the shock to one of the batwings..... probably the out board wing, were it not too much a**ache as the inner is supporting the spring and doesn't need any additional loading.... though, you could use the inboard wing.