I suppose that Gar are different depending on species and location but for Florida were I targeted them extensively and caught some I found: the only hook that gave me consistent hook ups
is the old double salmon hook and by the way that's legal per IGFA rules whereas rope flies aren't. I also found them semi-aggressive
when you present the fly right. They hit with a side wise slashing strike and prefer the fly moving away at an oblique angle close to the side of their mouths.
They snap shut quite tight on a fly and given their teeth, lock down on it so a heavier weight rod is needed to set the hook coupled with a firm slip strike.
To float that hook somewhat, you need some deer hair trimmed tight to give a nice, near surface, submerged, presentation. Muddler style.
I added doll eyes, again some float. The eyes last a strike or two and need to be replaced after each trip when lost. Sight fishing is easiest by targeting Gar that are feeding and sunning quite close to the surface as they are prone to do.