yes 63 ohms, each of four speakers.  I got these readouts at the
speaker plug (which connects to the radio).
So there is also resistance of a shielded speaker cable which goes to
the trunk, and then it connects to the speaker wires.
I should have measured directly , at the speaker..  i'll do it
tomorrow.

I also checked for the shortage to the ground or speaker to speaker,
but all the speaker wires are separated,  no shortages.

My ohmmeter must be OK, because in the other car i measured 4.5 ohm for
each speaker, which is standard.

As i wrote those 63ohms Lincoln speakers play pretty good with an after
market radio which i got with the car.

omg!  you're right!  its 6 ohms,  not sixty.  Sorry for this!!  (the
battery in my digital meeter is almost dead and it just didn't display
the coma.)

Bob, this is very interesting.  Although i can't imagine that switching
functionality because i don't have the factory speaker plug.  I made a
simple diagram of what i have now:
http://xs.to/xs.php?h=xs1108&d=06441&f=diagram.gif

i connected ISO speaker socket (8 pins)   to this radio according to
this pinout:
http://xs.to/xs.php?h=xs1108&d=06441&f=diagram.2.gif

There is a jumper plug attached to the CD changer socket, it shorts
1-3-5 and 2-4-6 pins,  when i removed it for a moment, there was no
sound at all.  Maybe those pins should be shorted differently, in order
to switch the radio into 'non premium mode' ??

There is also some pin (like a small plate)  between CD-changer socket
and speaker socket,  but it seems to be grounded to the chassis,
although i read somewhere that there could be +12 when the radio is
turned on.

I also found out, that minus speaker pins:  FL-, FR-, RL-, RR-  are not
grounded to the radio chassis , and are not connected together neither,
but maybe thats the design and its correct.
I checked the other radio (different brand) and minus signal outputs
were grounded.

Thanks for any help resolving this issue,  if any pictures would be
helpful let me know.
Tom