Might be worth taking out a tape measure and checking the width of the rails on your '65, then dropping by your local trailer shop or RV supply place and having them look for something to fit.
Some places won't sell you a hitch if you say you're trying to put it on something older than a '72. Liability, etc. so it's best not to mention the '65. Find out what vehicle the hitch is made for, then tell them that's exactly what you have...
-Boyo
