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.
Besides, chances are good that the Coronet already has an 8 3/4 in it, so maybe just compare rear gears if they're both 8 3/4 and use the most appropriate ones for your use.
