Answer:
Yes, Harlowe should sue for specific performance of the contract.
Specific performance is a legal remedy in contract law where a civil court orders the breaching party (seller) to perform their part of the contract.
In this case, Harlowe will probably be able to get the painting since it is a unique article, but it will be harder for him to get the chair. He might be able to get the seller to deliver it to him, but since it is a common article, he could find a similar one somewhere else. But that is not the case of the painting, which is not a common article and it cannot be found somewhere else.