Hi See another 5 speed box on the horizon,
Ok just to clear up some detail, from memory.
when i got my kit that complete shaft your showning is not included, what it is showing i beleive is how the parts mate together. The main and cluster shaft stay in the box and you work from the back of the gearbox and remove the rear casting that has the selector running through it.
Have you got your kit and is the cluster shaft included? if not great makes life easier.
once you remove the rear casting you need to remove the top selector rod and DO NOT drop the ball bearing inside or then you will need a stripdown including the differental "you have been warned" remove all detent balls and interlocking detent balls first to play safe.
you need to remove the second gear cluster on the rear, this will require you locking the gears together just select 3rd and 4th together and this will do it. the speed drive you remove will need to be slimmed down by about 1.5 mm but you will have to check on the instruction to confirm how much as i dont remember but it is hardened and needs to be done in a machine shop. the rest is easy and just check clearances on things as you assemble. once fitted make sure all turns and selector works with out binding as i found this required modifing, and if i remeber right the middle selector fork needed to be modified but you see this when testing the box just a file will do this. once the box is fitted to the car the coupling link needs to be shorteren by 37mm and the gearbox strut will need to be modified to clear the casting or it will rub on the gearbox. I said a day and that is easily done in a day, a pro can do one in 2 hours so is easy job but follow instruction and hay presto all done.

smallcox