Same part on 55-58 Pontiac and mid-50s Olds. I see them on eBay often, but today there is only one.
Search eBay for "c761748r" for the rubber mount or "GM 529880" if you are looking for the metal piece that mounts between the timing cover and the rubber mount.
I'd get both as I did have the metal piece break on my '57 GMC V8. Fan hit the shroud on gentle acceleration and left turns.
'57 GMC 102, Original 347 V8, HydraMatic, 3.08 rear gear, added A/C, disk front brakes, HEI, AFB carb, '98 Honda Black Currant paint. T-boned and totaled 10/12
'52 GMC 152 Stake Bed, Original 228, SM420, added A/C, HEI, disk front brakes, '67 Chev 3.55 rear gear. Gets used as a real truck.
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