Forget the body lift - like anything it CAN be done, if you throw enough money and time at it, but you have correctly pointed out the problems. You have several realistic options.
1. Replace your sagged springs with new ones, replacing the worn out bushes at the same time - it is likely that this will raise it a surprising amount, depending on how bad the current springs are.
2. Fit parabolic springs. This will cost a little more than (1) but will raise it around 40mm above standard and greatly improve ride and articulation. Needs recommended shocks.
3. Fit military shackles. Strictly these should be accompanied with raised spring hangers, but a number of people have got away with them by themselves. The simplest and cheapest but upsets the castor angle at the front and the prop shaft U-joint angles front and rear.
4. Go to spring over axle. This involves very substantial modifications, and is unlikely to be approved by any engineer, as it involves serious problems with steering linkage and prop shaft angles, quite apart from stability questions.
Note that some states have a blanket ban on any lift over 50mm regardless of engineering approval, and even this much will involve modifications to the flywheel cross member to clear the prop shaft, at least on the four cylinder version.
As far as later spring fits go, Series 3 springs fit, as will some Series 1, but while the specifications differ for different models, they are all very similar height. I would suggest you look at (2)
1986 110 County 3.9 diesel
1970 2a 109 2.25 petrol