But when you trade in a vehicle used for business for which you claimed Section 179, you have to report the gain.  Even if the dealer didn't give you a piece of paper telling you that it was reported to IRS.  

I would find out if there is a secondary market for those intervals they are selling at $290K.  You might find one that sells for $200K, and you can figure out from that what the trade-ins were worth.  We have a tax on income, not on pieces of paper.