When I had mine 'professionally' fitted it came with a small piace of 3mm steel and 2 tek screws into the side of the a pillar, see below.
This lasted until the first time I lent on it in a rut and it ripped the tek screws out, so I put in some bigger tek screws and they lasted a couple more months before breaking the bracket and ripping the screws out of the guards

So I made up 2 mounts out of 5mm steel, making them into T pieced shapes. So now they mounted to the sides as well as the front of the a pillar with the biggest tek screws I could fit. Below is the only detailed pic I have.
That lasted till Mud Guts last year when I clipped a tree, which ripped the screws out of the snorkel itself leaving the mounts behind
So now I am snorkel less and will probably stay that way as I tend to shy away from big, wet holes these days.