Who would be the power players in a Liberal-SDP-Conservative government, do you reckon? I might give a timeline like this a go.
As it happens, I too thought about doing this, though maybe more for a series of wikiboxes. In my particular scenario, the Alliance had something like 260 to the Tories 130, and they formed a government with Jenkins becoming PM. As compensation to the Liberals for being the largest party, they got both the Treasury and the Home Office, with Steel taking the latter, in part because of his lack of economic experience, and in part to enhance his party's standing by giving them two important people at the top of government. Richard Wainwright, their economic spokesperson became Chancellor, followed later on by Alan Beith. The Tories, who were in the weakest negotiating position, got the the Foreign Office, which was given to Heseltine, while Whitelaw became First Secretary of State and Leader of the House. The other members of the gang of four got some middle sized portfolios.
I'm not sure how plausible that all would be, but I definitely think Owen would become quite important, as an opponent of close ties to the Liberals, he'd probably pressurise Jenkins to ensure the pact ends with the implementation of STV, and probably want to pull the party to the right a bit, given his sympathies with Thatcher in OTL. He'd probably be seen as a likely successor as well, given Jenkins was getting on a bit, so I'd think the Owenites would become a significant faction within the SDP.
With the Tories, it depends on who holds on there seats. On the right, Tebbit or somebody would probably become an important figure, though I had the Monday Club types not taking seats in the cabinet, because I just couldn't see them as sitting alongside Jenkins and Steel. Maybe the monetarists like Lawson, Brittan, and Howe would. The Liberals would have the largest intake relative to their previous number of MPs, so they would be more unpredictable, particularly given that their existing members had made their reputation as being independently minded, and they would make up the bulk of their ministers, at least to start with. Cyril Smith and Michael Meadowcroft were critical of the alliance in OTL, maybe they would be prominent in any ant-steel factions, though whether that is from the cabinet or the backbenches I don't know.
The other two members of the Gang of Four are always going to be important, because of their status. You'd also have whoever Whitelaw gave the important jobs too in his administration becoming more prominent over OTL. Prior and Gilmour are good examples. Alan Beith and David Penhaligon were both touted as potential Liberal leaders at the time. So in short, you'd have an awful lot of power bases.