Its entirely a personal choice but if the bike gets little use maybe it would be better to just fine tune the existing setup as these bikes are perfectly capable of running smoothly and reliably on a std setup.... start with new plugs, points, condensers, check the coils, caps and leads (new coils and leads will only set you back 50 quid or so...), set the timing. Balance the carbs, check the compression. If all ok it should run smoothly.