Great films, thank you for posting the links.
Re whether it would be possible to do the journey through Africa today, the answer is maybe, but not in a car ! If the political instability does not get you, the roads / bridges in many countries are worse than they were in the 1950's and 1960's. In 1993 I took a then 30 year old Landrover from Cape Town to the then Zaire without much trouble, passing through all of Southern and East Africa before going to Central Africa. The minute one went off the main roads, the roads were very poor and four wheel drive / low ratio and high ground clearance became critical. The other key issue is simplicity, in terms of being able to make running repairs, and also fuel - most African fuel is too low quality to use in modern engines, but older / simpler vehicles are fine.
The journey could not go further than Central Africa (plan had been to drive to London) due to Islamic fundamentalists threatening to kill all foreigners in Algeria, so this limited the ability to cross the Sahara and no transit permits were being given. If anything, this has become a much bigger issue today than it was 30 years ago. From start to finish, I was away for 7 months, and had many memorable escapades.
More recently in 2010 and afterwards I flew myself on a few occasions between South Africa and London - much easier to cross the Sahara at 12,000 feet or 35,000 feet (depending on whether I was flying a pressurised or unpressurised aircraft), than battling through the deserts with lots of unfriendly armed people !
I think the late 1950's / early 1960's (before I was born) were the heyday of being able to do long distance overland travel between Southern Africa and Europe