My Disco has had a 2" lift on it for over 15 years now. Aside from the adjustment to the speedometer, there's nothing else effected that has shown itself in the last 15 years and the benefits of clearance far outway any desire to keep it original with respect to OEM.
While I completely respect ones wishes to keep a truck in original condition, there are many good reasons to modify the clearance of a truck. I spent many years in MA, Maine and New Hampshire having to get in and out of nearly impassable locations for IT work I did back then, and there is not a chance in hell I would have been successful without the additional clearance, larger tires and a winch.
I would point out as many just did that at 3" if you are going with suspension only and not a combination of body lift and suspension you might run into some steering and driveshaft change/adjustments. (Again a massive amount of opinions on the subject)
Depending on your needs you might want to consider a cheap spring lift at 2" that will cost about $20.00 and your labor and see if you're happy with that before you go making an investment into a 3" lift.
You can go to a salvage yard (Or contact Paul Grant) pull the rear springs out of like year model, install them in place of your front springs, which give you a 2" lift in the front and then buy hockey puck 2" spring lifts for the rear on eBay for around $!0.00 install them and you're all set at 2". ( I went this route, except used solid steel 2" square stock and drilled out the mounting bolt holes. The eBay spacers are inexpensive and a lot less work)
I run 265.75.16 snow tires with that 2" setup and have never had a problem and have been very happy with the overall performance. By that I mean to say there were no adverse effects in any way to the drivability or the enhancements of the vehicle than before I did the lift.
You should also do a thread search (Before you post a question
) and you will find many postings with many opinions on the different options available.
Your posting really is not telling enough as to why the 3" lift size and that will also make a difference in the recommendations you get. So maybe a little more about why a 3" lift would help.
Some search parameters that will help are:
Terra Firma lifts
I was on this one today that might be helpful as well: