Doing a rack on wet car is a recipe for losing knuckle skin...
The hydro hoses are a tad too short and the 'frame won't drop quite far enough to make it easy - it's possible, but tricky and painful.

if you have the ability and facility to depressurise and repressurise the system, it will make life a lot easier - BUT, you're dealing with an old system which has foibles and may be better left untouched...

Your choice.

I have never done a steering rack in a wet car but i think the hoses should be long enough to drop the sub frame the small amount you need without disconnecting them.

As Chuck has stated there are no centering holes in the floor on MK I's i would center the rack off the car before installation.

Thanks Malsal,one other question,wet supp. do I have to disconnect those hoses?

"As the U bolts..."  That paragraph will save you a lot of time and trouble.

Regarding the centering, since you are working with a Mk I, don't expect to find the opening on the other side.

And if you haven't decided, yet, consider converting to a Mk II+ rack, changing the steering arms to match the later rack. It will mean having the toe out reset, but well worth it.

Jack up the car and put it on jack stands. To minimize damage from the stands i use a thick piece of plywood under the front floor corners where it meets the sills (not normally supported here but you have no choice when doing a rack). Remove the front wheels and loosen the locking nut on both tie rod ends then disconnect both tie rod ends from the steering arms. Support the engine with a jack under the gearbox with a piece of thick plywood also. Disconnect the stabilizer bar from the engine. Disconnect the brake line from the master cylinder down to the sub frame. Undo the four suspension tower bolts and two front panel bolts (loosen is sometimes ok) along with the four floor bolts. Now you can lower the jack and the sub frame will drop down. Lift up the carpet and remove the pinch bolt on the bottom of the steering column and steering column retaining bolt under the dash rail, carefully pull up on the column and drop the column onto the drivers seat (you may have to disconnect the column wiring). Undo the four rack bolts in the bulkhead/floor section and remove them. The steering rack is now ready to remove.                                                                                                                                                                                                    
As the U bolts that hold the rack in place tend to spring out when removed make sure they fit back into the holes. This can be done from inside the car and if they have sprung out slightly just tweak them in a vice until they fit. This makes re installing the steering rack a lot easier.

Do not tighten the rack up fully until you have installed and tightened the steering column first.

Remember how many turns it takes to remove the tie rod ends and re fit them the same number of turns.

Make sure the rack is centered by removing the plug in the floor and the plug in the rack on the passenger side and turning the rack left to right until you see the locating hole then insert something size appropriate to center the rack and steering wheel.

As the Haynes book of lies say's "re assembly is the reversal of disassembly".

There's no "Trick" to change the rack unfortunatly but it's not difficult. You can support the engine and frame and just unbolt it and allow it to drop until you can wiggle the rack out and the new one in.

Looking for some tricks on replacing my streering rack on my MK1 mini.Are there any videos out there?