+1 on the Marti.
According to the Ford Buyer's Digest of 1967, the GT Equipment Group "Makes Mustang even more the "Car-man's Car" with more performance gusto. Available on any model. Includes Front Power Disc Brakes, 4" Fog Lamps, Special Low-Restriction Dual Exhaust System and chromed "quad" exhaust outlets with the 271- or 320-hp V-8, GT Side Stripes, GE ornamentation on gas cap, special Wide-Oval tires, higher-rate springs and shocks and stablizer bar. $205.05".
Per the same digest, a few related items from the order list:
289-cu. in., 200-hp V-8 $105.63
289-cu. in., 225-hp V-8 $158.478
289-cu. in., 271-hp V-8 (with GT Equipment Group only) $433.55
390-cu-in., 320-hp V-8 $263.71
Cruise-O-Matic with 200-, 225-hp V-8 $197.89
Cruise-O-Matic with 271-, 320-hp V-8 $220.17
GT Equipment Group (with V-8's only) $205.05
Competition Handling Package (with GT Equipment Group only) $388.53
Note that any V-8 (even the 289-2V) was available with the GT.
In 1967 (only) a GT with an automatic transmission was badged as a GTA on the fenders, GT on the gas cap.
Standard gas cap was twist on; the pop-open cap was included with the optional exterior decor group.
The interior decor group (deluxe) and style steel wheels were separate options for GT's and non-GT's.
I've seen only one 1967 with the Competition Handling Package. Original owner, "Bullet" green fastback, hi-po 4 speed. The wheels were 15" with full size hub caps (looked like from a T-bird). Original spare tire.