LOL, my 83 is a one-wheel wonder also, LSD died long time ago and diff makes grinding and whine when driving. Like the 4.10 but may pull a 4.30 out of junk 85 with 105k on it....what kind of gas mileage do you get with your car????
not sure about the gas, but you should either swap in another used mkII diff for the cheaper option or contact Weir Performance in the vendor section for their LSD rebuild kit. You can also send it out to them for a rebuild.