Could Clark become Premier instead of Don Getty? King Ralph?
I don't see why not. If he could convince Albertans to give his party all their seats in the federal Commons, he should be able to convince them to support his leadership of the provinicial PCs.
A few things though...
If Clark were as "red" provincially as he was federally, he would best ascend to the leadership in 1985, like Getty in OTL, rather than in the early 90s, like Klein. Assuming you think that the early 90s slash-and-burn policies were inevitable(and even Laurence Decore was championing them in OTL), I don't think Clark would have had the tempermant or the inclination to put them into practice.
And again, that's assuming that Clark provincially is a Red Tory. If he was representing a rural riding(as in OTL), without the tempering influence of federal politics, he might just have pandered to the right-wingers in his home turf.
Also...
Assuming Clark runs for the leadership in '85, but everything else is the same, he's up against Ron Ghitter, a Calgarian most recently associated with anti-racism endeavours(and widely despised among the religious conservatives), and Julian Koziak, a centrist from Edmonton, popular among ethnic voters. I wonder how Clark positions himself in that crew.
Finally...
The Maureen factor. Ms. McTeer may be a lightning rod for anti-feminist religious Tories, specifically the old Alberta Report crowd who villified Ron Ghitter. Not sure what would happen if Clark got smeared as Maureen's beeyatch.