I'd recommend the JBA 6610. I can't attest to the fit on a 65. I have them on my '68. The specs do say something about the 65 hand brake pivot.
I had Hooker's on it but I didn't like how low the collectors were. The Hookers were 1-5/8" tubes. The JBA are 1-3/4" which are better for the AFR 185 heads.
The Hookers looked wimpy. The JBA's look meaty.
The JBA are also a much easier install as far as header bolts, spark plug wires go.
There are no clearance problems anywhere with the 6610 for my application. They fit much higher up into the chassis and are at least one full tube higher at the collectors then the Hookers are.
Some will argue that there is no difference in power between the header primary sizes. I look at it this way, the bigger tube is worth 1/10th in the 1/4 mile. That means they are making more usable power.
I sold my Hookers for $550. There were a lot of tire kickers bit chin' that headers were only worth $150 but that was in the previous century when Cobras were $2500 cars.
http://www.jbaheaders.com/feature_pages/65-70mustangnew.aspI can post some pictures later if you want to see them on the car?