wall 33 and an adjustment end 35 the bottom plate 31 has an aperture 34 through its center for receiving the upper end of the alignment pin 15 a forward arm 36 is affixed to the forward wall 32 proximal the adjustment end 35 of the cradle 17 and extends below the bottom plate 31 the forward arm 36 has an aperture 37 for receiving the forward end 28 of the threaded stud 24 a rear arm 38 is affixed to the rear wall 33 proximal the adjustment end 35 of the cradle 17 and likewise extends below the bottom plate 31 of the cradle 17 the rear arm 38 has an aperture 39 for receiving the rear end 29 of the threaded stud 24 see fig7 when assembled the cradle 17 is supported on the upper surface 21 of the support plate 18 with the upper end of the alignment pin 15 extending through apertures 27 and 34 see fig3 and 6 while the support plate 18 is substantially stationary with respect to the leaf spring assembly 13 the cradle 17 is pivotable about the alignment pin 15 within a limited range of motion the threaded stud 24 extends through the apertures 37 and 39 in the forward arm 36 and rear arm 38 and is welded into position on the lower surface 22 of the support plate 18 at the adjustment end 23 the forward nut 25 and the rear nut 30.