And disconnect the reversing light switch wires!!
I hope it is as easy from below as it sounds! This is probably the approved method for gearbox/clutch removal though I have never done it this way and, as these are heavy gearboxes, I think it would require quite some dexterity and strength while rolling around on the floor if the car can't be raised on a full hoist.
Removing the exhaust manifold can also become challenging if, as on my later cars, it is fixed with 8 smallish Allen bolts that are seized and easily strip. Also, the full exhaust system cannot be dropped down from the car without splitting the middle and rear boxes as it passes over the rear axle with a box fore and aft. However I would think it can be swung to one side enough to get the gearbox past.
You might want to consider the other approved method of removing the entire "propelling unit" (i.e. engine, gearbox and subframe) by undoing the 6 subframe mounting bolts and raising the car off it though this involves disconnecting more stuff, including steering column, brake lines, electrical and cooling/heating plumbing and you still have to undo the exhaust (bot not remove it). It may also provide the opportunity to attend to other jobs around the engine/subframe and clean up the engine bay itself.
Even when approached from above with the subframe out like this, the gearbox is a bit of a tight squeeze to remove from the subframe and the lower crossmember under the box still has to come off.... but access and visibility are generally better and the heavy gearbox remains below your head at all times!
Here is a pic of mine going back in (and for some reason without driveshafts or wheel hubs fitted) so you get the idea.
It actually came out a different way as a clutch problem (which I decided to approach by removing the engine - also a tight squeeze but again working from above) turned out to be a gearbox failure (so the subframe and gearbox followed later). In this pic the old gearbox is still in the car and the replacement is on the floor.
