A quick update:
(i) Yesterday we used the electric drill in the distributor hole as suggested and got the oil to come out of the rocker holes, but only just - it just seeped out of a few holes but didn't spurt out. Is that what should happen? We don't want to run the engine for more than a few seconds until we are sure about this.
(ii) Can anyone post a pic showing how the throttle linkages go together on our kind of RHD Chev? All the Google pics show only LHD linkages, which are completely different. One of the linkages crosses from the accelerator pedal behind the engine to link up with the carby, but we cannot see where it fits or what it should be attached to (maybe the firewall?) We didn't take enough photos and now cannot remember.