When searching for parts online, you should give Rock Auto a try, I have found many wholesale closeout prices on parts including calipers and rebuild kits.

My calipers were nasty, had been sitting for 5 years before I got the car - I rebuilt all 4 - a bit of a pain but it's a hobby I guess. You should be able to get calipers cheap.

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1969
Model 220 gasoline
Chassis: W115.010