Maudling was the obvious choice, Powell pre:Rivers of Blood didn't have the profile or sufficient support to win. The big question is who would the left put up in the absence of Heath?
Talking about 'left' and 'right' is partly anachronistic in this period, but Maudling was probably to the left of Heath. There would be no 'left' faction looking to put up 'their' candidate. Maudling would be a shoo-in and it's not even a given that Powell would stand after the previous year. Though you admittedly have to make an allowance for Powell's character and limited political judgement in that respect.