Bend the side baffle
I have the same engine, and had the same problem when fitting the snorkel. The snorkel is just a bit too wide. What I did is to bend the side baffle outboard slightly to make enough space to fit the snorkel attaching bracket. Per Van's drawing the side baffle should be bent inboard, but it won't work for the stock horizontal snorkel. If you are using Van's cowling, bending outboard shouldn't cause interference issue between baffle and upper cowl. I know some builders cut the snorkel and re-glass it to make it fit. But I don't like fiberglass work that much. The only problem with bending side baffle outboard is you have to use a 0.125" shim between baffle and cylinder where they are screwed together, and seal the bigger gap with more sealant.