The current version of the code assumes that McAfee will be installed into /usr/local/mcafee or /opt/mcafee. If you install it elsewhere (e.g. /usr/local/uvscan) then you will need to edit the paths at the top of the mcafee/autoupdate and mcafee/mcafeewrapper scripts, and change the location of mcafeewrapper in the mailscanner.conf file.
Look out where you install the DAT files for mcafee, as the shipped mcafeewrapper script assumes they are installed into /usr/local/mcafee/dat.
Other than that, all the code to support McAfee is now in the same version of the code as the Sophos support, so all you should need to do is ensure that the mailscanner.conf settings "Virus Scanner" and "Sweep" are set appropriately.