If you deposit it in small increments over a period of time (structured deposits) you will cause your account to be red flagged and you will be audited by the IRS and most likely investigated by the FBI. This is done to stop drug transactions, which are all cash, and movement of funds for terrorist activities, again all cash. Fill out the form, make sure you keep a copy of the bill of sale for the truck. You only pay taxes on income (profits) if you sold the truck for less than you paid for it you shouldn't have a problem.