Ok situation is I have a 2004 Mustang GT paid off that is my daily driver year round in New England.

I can get a 2007 Tacoma in brand new condition with 40,000 on the clock for around $15k from a family member (dad). $3,000 cash down then a payment system to him .

Is this a good idea? Figure I can store the mustang in the winter and use the Taco.

Yes, but I hate mustangs and love tacomas so you need to take my response with a grain of salt.

Mustangs as daily drivers in New England?
Snowy on ramps are fun huh?
Look at my screen name and ask me how I know.....

Car payments are a bitch, but only you can answer if the truck is right for you.
I bought a Jeep. Then modified (highly this time) my fox body.
Nothing like pulling it out of the garage on the first sunny day of spring
and launching it at 5500 rpm with the front wheels up in the air!!!