I can't remember specifically for the 65 Mustang but on my 64 Fairlane there was a little 3 or 4 inch piece of rubber hose between the fuel tank and the hard line that delivers the fuel to the carb.
In my case the car would run ok up until a certain speed then cough and fart and barely make it home. Turns out that that little rubber hose had basically crystallized inside and was severely restricting the fuel flow.
Just something easy to check while you're 'cooning around looking for the problem.
Governments are extremely dangerous.
Death, imprisonment, theft of property
and loss of freedom will result from
giving them too much power.