Are you sure it is the caliper and not the hose?
I spent several years on calipers some 25 years ago on my 164 to no avail - turned out my brake line was
swollen shut and acted like a czech valve. Brakes would apply fine but would not release.
You wouldn't believe how fast it wore pads and disks and the smell was like a burning electric motor!
New rubber lines stopped the problem immediately. I still have the original calipers on my 69 164.
One of them (left rear) has been rebuilt twice (new seals).

You can try bleeding the front wheels only. If it works, fine. If not, do the whole thing.
Use a pressure bleeder!
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George Downs, Bartlesville, Heart of the USA!