Amery as PM..
The obvious POD would be for Quintin Hogg to win the Conservative leadership in 1963 . Hogg wasn't in the Commons but was a good friend of MacMillan (and was his son-in-law) and might have been the anointed successor.
I suspect as Prime Minister Hogg (once back in the Commons) would have made Amery either Foreign Secretary or Home Secretary. I suspect Wilson would still have won in 1964.
Amery might have challenged Heath from the Right in 1975 instead of Margaret Thatcher and could have become leader and later Prime Minister.
There's an awful lot of ifs, buts and maybes and is marginally ASB.