Add a gift entry type for Vehicle or Boat so that there is a field for Appraised Value then one for Sold For/Sale Amount so that the Fair Market Value (FMV) can then be determined (i.e. the database would complete that value field). Then you can edit the Real Estate section with an Appraised Amount field and FMV field too. The IRS will only allow a donor to deduct the FMV, and a nonprofit will obviously only be able to use the amount the item sold for (which is the FMV).
Okay, I goofed above - the nonprofit can only use the SALE amount, but for good donor stewardship, would then have the FMV if there was ever a question as to its amount.