this is a vacuum advance and retard .
you will have 2 pipes coming out of the distributor diaphragm ?.
one goes to a pipe next to carb base and the other goes to a fitting on the inlet manifold almost underneath the air filter box on top of carbs .
you set the static ignition timing at a certain RPM , i think 750-850 idle rpm and at TDC or 6 degs advanced on the front damper pulley markings .
its been a while since i had my range rover but it had same configuration as you mention .
as soon as you touch the throttle you should see the advance kick in and youll lose the timing mark when viewed by strobe light .
hope this helps