Since you are keeping the original sway bar up front, I'd suggest 1.0" t-bars.

My 67 Satellite ran .96 t-bars, 1.125 sway bar and a small block with XHD leafs. It was pretty well balanced. With the B engine, smaller sway bar, and heavier overall vehicle, you might want to make the t-bars work harder in the combination.

FWIW, I've seen XHD springs called out at around 140#. 120# was typically the rate of the four leaf, albeit thicker leaf, oval track springs.