Cam for 69 gts. Recommendations so far.
Howards is the older 214/224 with extra lift.
Hughes is bigger duration and lift
For Lunati I'd go to the 03 voodoo. Springs might be an issue because Lunati recommends a double spring IIRC. If you can find a decent single spring with correct rates, this is my suggestion.
JMO, I would not use the howards, barely a jump from stock. The hughes would be the smallest I would use.
The car has a 4 speed and gears, you can get away with a slightly larger cam. Get the idle tune up right and the lunati 03 with an intake/headers will be a stout little runner.