Glasgow to mull of kintyre is just over 3 hours over a busy enough single carriageway as it is, the rest and be thankful road was closed for awhile due to a major landslide.
port Patrick is roughly 2 hours down mostly motorway and duel carriageway, while passing through east (i think) and south Ayrshire council controlled areas where the roads are actually pretty decent.
South of Ayr there’s 60 odd miles of some of the worst A roads in Scotland before you get to Portpatrick. None of it is motorway or dual carriageway. This would all have to upgraded.