For 2013 and later, a very strict set of tests outlined in SAE J2807 must passed. I'm assuming the standard Pacifica wouldn't pass one of them without beefing up cooling and alternator. Chrysler didn't want to raise to cost to all vehicles, but needed to say they have at least 3500lb towing. So they have a package for people like myself, who want to know it has passed J2807 and keep the price lower for others. Here's an article on J2807, SAE J2807 Tow Tests - The Standard (motortrend.com), which shows the test is very aggressive. Most people will never hit these conditions. Monitoring coolant and trans temps is always a good idea towing and especially necessary if you are towing with an aftermarket hitch.