Mine is 27 5 /8 x 19 just barely fits(outside of tank to outside of tank) and actually touches the battery tray on the drivers side and frame rail on the passenger side. The battery tray is keeping it from going any further toward the frame rail on the drivers side.I would measure very carefully if you are going up to or beyond 27 1/2 inch unless you have relocated the battery and in that case 28 should be no problem. The opening for the rad fins should be 22 1/2 which leaves 2 1/2 inches of tank on either side.