The North Coast 500 looks absolutely outstanding, check that out if you havent already! Although this isnt the time of year for that tbh. Ive driven most roads in the central region, would recommend anywhere really between Stirling and Inverness, West side along the Lochs, A84 is a good run up to around Killin, then you'll be on the A85, can take a couple differnt routes and come out a t Glencoe. A811 & A82 is another grear route, down the A83 and up the A816 along the coast and you'll come out at Oban. Used to be a great run up to Nairn before the fuckin average speed cameras