I believe that kit #26133-07 includes an adaptor plate that goes behind the oil filter for the sending unit to screw into.
You will not need that kit if you install the sending unit in the oil pan using the pipe plug hole next to the oil drain plug (item # 15 in the attached link)
You will need an reducing adaptor for the sending unit to screw into the pan. I believe the correct size adaptor needed is 3/8 NPT external-1/8 NPT internal thread. I would pull the plug and take it along with the sending unit to the parts store to match them up with the correct adaptor.
2012 RGU / Big Blue Pearl / Fuel Moto Ceramic 2-1-2 Headpipe / Fuel Moto 4.5" Pro Touring Mufflers / Fuel Moto Stage 1 A/C / Power Vision Tuner / Heritage Bars / Seat Mod by MCC /Rider and Passenger Bead Riders / BAL Tail Light / 12" & 14" Windvest / Sancho's wings / Iron Aces Phone Mount / Rear Fascia Upgrade / Avon Grips / Mean Mug by Gas Capital Customs