There was quite a bit of interest shown in the car prior to the auction. R-M started the bids low, price was quickly bid up, three bidders still involved at $60K, two bidders continued and hammer came down at $75K. 10% fee makes the buyer's total $82.5K. Car is going to a good home, a serious collector.
I think that bidders who play at this level probably know Abarth history very well, and may not be too concerned that a very rare car had a motor upgrade. Especially if they intend this car for driving, not sitting in a museum.