The dealership told me the 1958's have a little bit different of an ac system. no ventilated seats, cool box etc. so maybe why some folks aren't seeing the issue. but I would think if FE/premium actuators are bad, it would apply to all. also think it depends on outside temps for some reason.
my 1958 does the same as what's described in this thread. Auto does seem to work better, but manual is hot above LO. it is 20-30 degrees here currently though.