The Millweld 4" snorkel requires an almost L shaped cut out of the guard. I had a Nissan snorkel before fitting my Millweld and it required large amounts of panel surgery. Also if you are going for one with a RAM head the RAM is not a 4" rather 3" and sits inside the stainless pipe. See below for the difference.
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I should also mention I believe just about all 4" snorkel require large amounts of panel surgery just depends on the manufacturer and if they worked out a better design that requires less.