How to distinguish a factory GT from a non-GT

This is a question that seems to come up on a fairly regular basis. I haven't gotten around to writing anything about this because a nice man named Steve Schwartz at Mustang Dreams asked me to help him out while he wrote something about this, and he did a very good job with the subject. But, it can't hurt to have the information in as many places as possible, so, here goes.

The GT package on a 65/66 Mustang included :
Front disc (non-power) brakes
Dual exhaust with the exhaust trumpets exiting through the rear valence, not underneath it

Special handling package: front sway bar measuring 13/16 in diameter, instead of the standard 11/16,
higher rating front coil springs and rear leaf springs,

heavy duty front and rear shocks:
64 1/2-65 front shocks were the C4ZF-18045-E
66 front shocks were the C5ZF-18045-B
64 1/2-66 rear shocks were the C4ZF-18080-A, -B, or -C

Quicker steering box gear ratio of 16:1 instead of the standard 19.9:1. The manual steering cars will have the HCC-AX tag, and the power steering cars will have the HCC-AW tag. All power steering cars, not just the GTs, have the steering gear box tag of HCC-AW, so, on a power steering car, this tells you nothing.

Rocker molding and quarter ornament delete. The GTs had the no rocker molding or quarter ornament because they had the GT stripes.

No running pony on the fenders, or the small Mustang script. They had the GT fender badge and the Mustang script down lower in individual letters.

GT gas cap on the 66s, standard gas cap on the 65s

Fog lights


The factory GTs, since they had the dual exhaust exiting through the rear valence, did not have the rear bumperettes, or any of the attaching brackets for those. They also have reinforcement plates inside the driver's side rear frame rails for the driver's side exhaust hangers, which a single exhaust car did not have.

The only 65/66 Mustangs that came with the GT package were 'A' code or 'K' codes. There were no 6 cylinder cars or cars that came with a 2bbl carb that also came with the GT package.

The GT package was not available for purchase until mid April of 65, and consequently, any car with a scheduled production date before February of 65 definitely did not come with the GT package. Sometimes, people will have a new door tag made with an unreliable scheduled production date on it, but, the sequential production number of the car in the VIN, the last six digits, are not something that a person could alter without committing a felony. So, you can generally trust that a lot more.

On a Dearborn built 65 Mustang, it would have to have the last six digits of the VIN be a number higher than 620,000.
On a San Jose built 65 Mustang, it would be a number higher than 180,000.
On a Metuchan built 65 Mustang, it would be difficult to argue that the production number was too low, because that plant started building Mustangs at about the same time that Ford started building Mustangs with the GT package. It was a little bit before, but not by much.

Here is the address of that article by Mr. Schwartz that I mentioned, which has pictures and stuff.
http://www.mustangdreams.com/Verify-1965-1966-Mustang-GT.htm