Rangie axles onto series 3

Hi, i've just been offered a pair of range rover classic axles and would like to fit them to my series 3 a)to improve the gearing b)to give me discs all round.

Just wondering whether it is easier to take the diffs/hubs/brakes and put them onto the series casing or weld series spring hangers to the complete axle?

Also would i need the rangerover master cylinder and servo? (i have a vacuum pump on my engine)

(a) improving the gearing is easy - just fit the Rangie diffs if the axles are all 10-spline jobbies.
Hubs are not interchangeable between Rangie axles and Series ones, so no go there.* You'd have to fit the entire Rangie axle - which although eminently do-able ... is a lot of work ... especially making sure the Rangie track rod (which sits behind the axle) doesn't foul the leaves on the Series suspension. If you're desparate for discs you might be better off fitting an aftermarket disc conversion - there's a couple around ... but they are on the pricey side.
Easiest way to put a servo on is potentially to go for one of the later Series 3 ones which will be a direct fit. (unless you're asking if your existing Series 3 master cylinder has enough displacement to operate the Rangie calipers - in which case I don't know - but I hope so because I'm in the middle of a similar conversion!)