I think you'll be spending a grand no matter which option you choose...unless you get a rediculously good deal on a Nova rearend...
New Posi unti = $400ish Gears = $150ish install kit = $100ish If you're gonna change the gears, you really oughta change the bearings while you're in there, too...and maybe the wheel bearings and oil seals.
it never ends.
I'm a hobbyist. Not a professional. Don't be hatin'!