Help with 182 gear selection problem

[Lofty27]

Hi I have a 182 which recently had a new clutch fitted since then I have had difficulty engaging reverse gear. I also have a shortshifter fitted which has worked normally before but has always a bit notchy and easily selects 5th instead of third. Has anyone found a reliable way to adjust the gear linkage? With the car jacked up I can select all of the gears from below the car by moving the gear linkage by hand. I need to get this sorted before the next trackday so any help would be much appreciated.