I wonder in this scenario if PET would be completely out of the picture. He's definitely going to play some kind of role in the Quebec Referendum, probably greater than OTL due to no obligations as PM. This might get him into provincial politics...perhaps Trudeau runs in 1981 instead of Claude Ryan as the head of the Quebec Liberal Party and wins over the PQ?
Just a thought...
Another thought might be this, with Clark leading a stronger Red Tory faction, perhaps the Liberal party drifts further to the right (no NEP will help in this regard). TTL could see Canadian politics shift substantially if the Tories remain dominated by Reds like Clark, all the while the Liberals drift further right...
However I don't see Clark as being able to weather the recession of the Early 1980's very well. This in addition to tensions over the constitution probably leads to him struggling come the next election in 1984. That being said I don't see the other parties doing that well either. Perhaps Clark is reduced to a minority government?
PET would never enter provincial politics because he despised the mentality of the bipartisan political class here (and Quebec politics generally as small-minded and insular), and pathologically loathed nationalism (except when it involved energy or trade policy) that both parties subscribed to in varying degrees. He dabbled in it in the 1950s through Cite Libre, though it cost him a potential job at U de M for doing that. Trudeau coming anywhere near the PLQ, let alone the premier's office, is downright ASB unless you change his views or personality in such a way that he's no longer recognizable IOTL.
Further to the right? They had been on the centre-left for 50 years, from Mackenzie King's election as leader to Pearson's retirement. Turner simply reverted to 20th century liberalism instead of socialism. Most likely everyone muddles down the same murky centrist path that Stanfield did in the 1970s- keeping in mind centrism defined as Nixonian, not Blairite. Blues eventually rear their heads: the Horner brothers in the '60s, though their economic ideas were internally given as much credence as Rob Ford was of winning the mayoralty last year by the
Star. In no small part because their personalities were parodies of Ford's.
Constitution: some sort of formula is worked out, but given the dog's breakfast of interest-group claptrap that was Charlottetown IOTL (Mulroney largely left Clark to his own devices and implicitly regrets in his memoirs, so Clark gets most of the blame there) I don't have much faith in him to produce a decent product.