Hello,
I have a 1964 Thunderbird and mine was leaking super bad from the rear of the intake manifold. I have very little experiance with american muscle cars. I have worked on import cars. I did the job my self and it was not that hard just time consuming. Make sure you have a engine hoist or some serious strong muscle to remove that 100lbs+ manifold. I will post this a link to this video that I found helpful its a great tip so that your intake seals correctly. Also I used "Rightstuff" Silicone and worked great I am now leak freeeeeee! :) Let me know if you have any questions.
Mustang Shop: Intake gaskets (easy stuff) - OperationMustang.com - YouTube