I have 2" HD springs & shocks on the front, 2" shocks on the back with bags with 2" spacers that the bags sit on.
My stock shocks were poo with the lift-defo change them.
Remember that spacers will not increase articulation, only height to allow a bigger tyre-you need to convert to coils to achieve that.But if you keep the bags, you still have the ability to go the extra height with the off road setting.
Whatever you do -DONT be tempted to go over the standard inflation of the bags to gain height...BAD news
Many will disagree but, you will throw UJ's if they are old when you do this. Remember you're changing the working angle that the UJ's have run at for however many miles.
I changed my rear UJ & donut & fitted an extended travel front prop with wide yokes.
I have also had to put spacers on the gearbox cross member...your prop will drop onto it if left untouched & could cause damage with the axle weight pulling it down.
http://www.landyzone.co.uk/lz/f8/disco-2-x-chassis-front-beam-96516.html
Youll also need extended bump stops, or space those too.
It drives fine on & off road with this set up, I know a couple of people who run it...although there will be people who tell you youll need correction arms...possibly but i have no need at the moment.