I seem to recall seeing an inboard spring set up that used a 1.5" offset link bar instead of swapping the entire sway bar to a narrower unit.

FWIW, E body spring perch center to center width = 46", A body = 43". Since the factory bar mounted to a plate set under the spring mount that centered off the spring perch, this should also apply to the sway bar link dimension.

You could always call Firm Feel and talk to them in greater about A body dimensions as well as ordering that rare, factory frame hung A body rear bar.