Challenge: Keep the Conservative Party a major force in Scotland.
some suggestions:
The PoD is in the mid-1960s Conservative Party reforms which ended the
Unionist Party - keep a Scottish "Unionist" or "Progressive" Party which has an alliance with the Conservatives in England & Wales, but has a separate organisation which is focused on winning in Scotland.
Ted Heath's government follows through on
the Declaration of Perth and the 1973 local government reorganisation creates a Scottish Assembly instead of the
Regional Councils model that was used in OTL (possibly in the context of regional devolution in England as well.)
The Unionists get themselves a leader with a decent amount of charisma and talent, someone who can stick up for Scotland against the 1970s Labour governments and is not a puppet of the London Conservative establishment.
Labour's official line is opposition to a Scottish Assembly / Regional Assemblies in general, however a number of members strongly dissent.
The SNP is more successful at taking Labour votes than OTL, and the SNP doesn't take as many Unionist seats in the North-East as OTL.
The first elections to the new Scottish Assembly are fought between the Labour Party, a "Labour for Devolution" Group, the Unionists and the SNP.
The outcome is a Unionist minority administration with SNP support...
... this is what I have so far. The other obvious thing is "no Poll Tax trial in Scotland" when you get to 1989.
You'd also need the economic developments in Scotland in the 1980s and 1990s to create more skilled manual and clerical private sector jobs, and avoid some of the sense of economic and social disintegration.
Scotland is never going to be the best area for the Conservatives, but if they can avoid losing support in the more rural areas outside the central belt to the Liberals and SNP, and keep a hold on middle-class voters in the big towns and cities they can hold on. The TL sketched out here will stop them being tagged as fundamentally anti- or un- Scottish.