This has been discussed previously here and a search should find the discussion. Apart from the point you raise about stability, there are serious concerns about not only the prop shaft angles but the steering linkage and the spring travel.
The front prop shaft will foul the cross member even with a lift of 50mm or thereabouts as on the One Ton and Australian military ones which have modified spring anchorage points and extended shackles. The U-joints on the front shaft and the rear one on an 88 will also run into problems if you raise it much more than this. 
Again, raising it much more than the above figure means the angle of the drag link will get too large, and will need some sort of a work round. If the lift is reduced to less than the spring thickness plus axle housing diameter, which is what you get by just putting the same spring on top of the axle, by reducing the spring camber, you soon get into restricted spring deflection - the upward travel of the axle is limited by the fact that the spring is now between it and the chassis.
Not to say these points cannot all be worked round, but it would be a very big undertaking and the few on this forum who have tried it seem to be less than happy with the results.
John
				
			 
			
		 
			
				
			
			
				John
JDNSW
1986 110 County 3.9 diesel
1970 2a 109 2.25 petrol
			
			
		 
	
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