Replacement body: Taxable or exempt?

We are a distributorship that typically sells new, taxable truck bodies wholesale to truck dealers. However, we occasionally also sell new, taxable truck bodies directly to the end user. Recently, a customer was interested in buying one of our bodies for use in his construction business. The customer told us that the sale of the body would not be subject to Section 4051 tax, because it was a replacement for a body that had been damaged. Is the customer right?