The Lock N Roll Articulating Channel Tongue Trailer Coupler # 336TS528 that you referenced is designed to fit on 2 inch wide frame channel. If you need a version that fits a 3 inch channel you'd want the part # 336TS508 instead. The 3 inch channel width is the most common size seen on trailers so this would be most likely your best option. The distance from the bolt center to the top of the channel is 3/4 inches.
On the vehicle side you'd then need the # 336VS501 which fits a 2 inch trailer... view full answer...
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