To add to the above, the number one priority is making a car reliable and dependable to drive on a long trip
So you want to take care of the critical things mentioned previously (cooling system, brakes, electrical)
Lots of owners and lots of mechanics overlook important details, and things don't get any attention until they break, preventative medicine is of utmost importance when living with a classic car that is 30+ years old and doesn't show signs of being maintained by the book
PS if you have trouble finding parts or information come here and ask (I drive and own about ten or so 240's and am familiar with how to keep them running and stay safe)