Personally I would say no.
As long as you keep an eye on the bits in there, like checking for air leaks in the induction side of things, checking dizzy vac pipes are in good condition, etc etc and also do sensible servicing, then you will be getting it as efficient as it can get. Rolling roads are more for engines that have lots to adjust on the fuelling side. Because our vans have fixed jet carbs there is nothing to adjust. As long as the carb is in good working order and the ignition system is also in good order and timed correctly (easy to do at home) then all should be OK. Oh and don't forget the air filter (lots of folks overlook them for too long).
Have you considered getting LPG fitted, everyone, including myself, highly recommend it
