Not sure if this'll be any help but I watched Clive from Blacksheep fit one to my Ninety yesterday.
The basic steps were,
1. Jack up the back end and put it on Axle stands and remove rear wheels
2. Cut the wiring loom and pull it back into the chassis until the end just goes in, then pull another foot.
3. Cut through the chassis and keep going back until solid chassis appears. ( a long way back in my case)
4. Clean up the chassis
5. Bolt the new crossmember in place and make sure it's level.
6. Pull the loom back out of the chassis. (I don't mean remove it but pull back to the rear what you pulled to the front before cutting.)
7. Weld the extension side plates on to both the chassis and crossmember, Clive welds inside and outside.
8. Curse because you forgot the cut the new loom exit hole
9. Cut the wiring loom exit hole

10. Weld on the bottom plates
11. Weld on the top plate for the non loom side
12. Take the **** out of rusty land rovers from Norfolk

13. Bring the loom through the new hole
14. Weld the top plate on the loom side but keep stopping and cooling the chassis to prevent the loom melting. Clive used compressed air.
15. Figure out where to weld on the brackets for the tow bar mount (Normally by fitting the brackets and using the pieces as a guide or, when you're a Norfolk Numpty that forgets to take the tow bar, measure the old one)
16. Weld the tub brackets in place.
17. Reconnect all the wiring and hope that the useless gits that did it last time did a better job than they did on mine! Thanks Simonnites, I need a new loom now!
I'm sure someone that actually did it themselves will be along soon with much better explain action than mine.
Oh, and don't forget to regularly curse rusty landies, Pressbrake clearly loves these vehicle
