Gear Knob as shown is a UK high spec one (RS3100 3000E GXL) Aust delivered GT had the smooth hard plastic type. However the knob you have was available and could have been dealer fitted (like fake side vents and bumper over-riders)
Rear belts as stated above, centre belt you need to remove the lower part of the seat the bolt holes are in the centre. Front belt top goes high up on the B pillar, the bottom bolt goes in the sill in the centre of the pillar. The buckle is bolted where the hump meets the floor pan just past the seat rail bolt hole, you may have to remove the carpet to see them all