To facilitate full experimentation in this area, the MS73 kit has been developed to allow accurate adjustment of rear wheel camber AND track. Adjustment of rear track can greatly influence the handling characteristics of the Mini. For reference, toe in gives straight-line performance/stability with more rear end grip (under-steer). Toe-out gives over-steer in corners, and less stability in a straight line - particularly under part/closed throttle conditions. Simple and effective caster/camber and tracking gauges are available from Mini Spares (Tool10 caster/camber gauge, TOOL11 tracking gauge) to facilitate DIY setting of geometry.
To fit these brackets, having jacked the car up and set on axle stands, support the radius arm assembly (place a jack under the drum) then remove the existing brackets by removing the outer radius arm pivot shaft nut and the four bracket to subframe retaining bolts. Now fit the main bracket in its place, ensuring the serrated face of the track/camber adjuster plate is against that of the main bracket. Place adjuster, as far forward in the adjuster hole of the main bracket as it will go. Hold in place by re-fitting the radius arm pin to bracket retaining nut and pinching up finger tight. This will ensure toe-in track setting initially. Fit the four bracket-to-subframe retaining bolts in their respective places and tighten up. To adjust camber - with the pivot-shaft nut finger tight, wind the adjuster bracket locating nuts up or down to suit - pushing the bracket up will add negative camber, pushing it down will add positive camber. To adjust the track, the pivot-shaft-retaining nut needs to be loosened so the plate serration can clear those on the bracket.
Also loosen the bottom camber adjuster lock-nut to allow sideways movement without loosing camber position. Moving the adjuster plate forwards on the serration will add toe-in on that side. Moving it rearwards will add toe-out. Each serration adjusts track by approximately 0.040" per side. Always make sure the pivot shaft nut is re-tightened after adjustments are made. Adjustment to one of the parameters may well slightly affect the other, so always check both after any adjustments are made.

NOTE - IT IS STRONGLY ADVISED THAT TOE-IN SHOULD BE SET IF THE CAR HAS TO BE DRIVEN ANYWHERE TO HAVE THE GEOMETRY SET. TOE OUT OF ANY AMOUNT WILL MAKE THE CAR VERY RESPONSIVE IN CORNERS - MAKING IT DANGEROUS TO THE UNWARY/INEXPERIENCED.