Don't have a Haynes manual but I know the refit is just a removal, I've done the change before just never on a 75 or ZT, the cars I've stripped down haven't had pinch bolts like these though nor had the same mileage. Last one I had stripped down and fitted coil overs on was my fabia vrs and that had 38k so everything moved easier. The 75 is almost on 78k so everything's dirtier and seized on lol.

I know it's possible to split them but I can't get the pinch bolt to move, hopefully an early start tomorrow and some brute force will see it moved.

Is it nut and bolt just below the shock absorber your trying to get out or the one at wishbone, better the nut and bolt higher up, theres a split in that one, you can put chisel in split ,open it up a bit while holding bolt with socket, loosen nut with another spanner ,soak it with plusgas or similar .

Its the bolt that holds the shock into the hub, it's a full threaded bolt not a nut and bolt set up.

Soak it with penetrating fluid then ,let it soak in over night, have you got impact screwdriver and socket, that might just be enough to move it, have you got any heat ?

Don't have heat but have an impact driver. There's not enough room though to get in and hit it?

Have you released the track rod end that might give you more acess to get socket on it ? and droplink

No haven't went too much into it yet as I spent a while trying to move the pinch bolt and then gave up for the night. Had a nightmare even trying to jack the car up due to a rubbish road surface causing the jack to sink and tip, luckily I had a wheel under the car and it landed on that rather than the ground! Got dents in the road surface so gonna get a bit of wood or a slab to put the jack on tomorrow and thankfully my wheels need refurbished anyway!

Be careful with the jack on a poor surface. I always use a metal plate on my driveway to prevent the jack sinking.
I also keep several off cuts of looting joists to place under the car when I'm working with a wheel off. I never trust axle stands.
As for that stud, yes it can be tight but as Walter says best to re move the track control arm as it allows you to swing the strut round a bit.
A good breaker is a must and use standard hex sockets.

It's usually fine, I've had cars jacked up on that piece of road before so don't know why it happened to sink in this time lol.

If push comes to shove my mate has 2 big bits of wood he uses so will get them off him if we don't have anything at the house. I'll try it again tomorrow, it's been soaking in release oil for quite a few hours now as well so hopefully an overnight soak in it will help then will try disconnecting the track control arm.

I ended up sawing down either side of the gap in the hub, then drilling down the threaded part of the bolt and using an easy out to screw the thread out then using a punch with the hub supported to drift the shank of the bolt out... new bolts and plenty of copper slip