360/727 in 81 Imperial

[<stealthloader@xxxxxxxxxxxx>]

  I have a chance to replace the 318/904 combination in my 81 IMP.  I have
done swaps in Fords & Chevy's but this will/might be the first for a
Chrysler.
  I have read in a few messages that the drivers side engine mount is the
same and the passenger side is different, is this true and if so what will
work?  Is the trans mount the same for both the 904 trans and 727? What
will work in place of the original if not? And lastly what about drive
shaft length?  I have never compared the two transmissions next to each
other but I think the 727 is longer.  If so is there another drive shaft
that can be used or do I have to shorten mine?  Shortening the drive shaft
might prove to be the biggest obstical as there isn't any place here in
southern New Mexico that does this.
  I am at the point where I need to decide whether or not to pursue this
swap.  The 318 in the car has 118,000 miles on it and the last time I had
it running (7 months ago!) it took 1.5 miles to get to 45 miles per hour!
So now is the time to rebuild or replace.  The 360/727 were rebuilt two
years ago and runs great.
  Any advise will be appreciated.

Dave U.
81 IMP