We recommend the TG112 for the Marlin Guide Gun, but it is only for those models with a front sight base ramp. If your front sight blade is dovetailed directly into the barrel, this set will not be a good fit for this gun.
We would also recommend you look at our 3/8″ metal front dovetail sights. These are available in two colors and three heights: measured from the bottom of the dovetail to the top of the sight.
One of these should be compatible with your firearm and provide great contrast and visibility.