Those old HS6's were one tough unit, the one on top will rust away and the Hs6 will still be there!!
Most of those were installed with the rfc liquid line, but not all, some had a expansion valve. There are a good many of those old units still in use, they seem to run forever. I recently changed one out for my Aunt, but did it the hard way, I removed the old unit first!! BTW her old unit was 36 years old, does anyone think ANYTHING we install today will last that long??