[twobjshelbys]

The decision to trade is one of taxes. Some states allow a credit on sales tax for the trade in value. For example, if you buy a $10000 car and trade in a $5000 car, you only owe taxes on $5k. However, this is usually limited to dealership transactions. Some other states exempt sales tax on private party transactions. You need to contact the Iowa DMV and figure out what their rules are.

If you are subject to taxation a $1 bill of sale won't cut it - they know about those hacks and have a minimum valuation that is often higher than the actual sales price.

When I sold my Cobra and bought my GT I ran the transactions through a cooperative dealer (for a nominal fee). The Cobra was officially traded in.

DO NOT ATTEMPT TO RUN THE TRANSACTION THROUGH MONTANA! Montana has no sales tax and almost zero registration fees. Hack lawyers try to sell you a Montana LLC and register your vehicle through it. Having Montana plates on a high value car is a red flag to most DMV cops and they WILL go after you for back taxes, penalties and fines. Ask a whole bunch of Colorado motor home and boat owners. Their vehicles were parked in public view on their lots and the counties around Denver got a whole bunch of them.