The 440 and 727 from the '66 Imperial will be good for a swap, but I'm not so sure about the rear end- besides being about 2" wider than the Coronet, didn't the '66 fullsizes still have the tapered axles? And didn't the Imps of that vintage use the oddball 5x5 bolt pattern? I could be (and probably am) mistaken on the exact years, but worth researching it a bit further.