It will go rich at high altitude and will appreciate being leaned out. Tuning instructions are always the same, regardless. Turn more lean until it starts to shake. Go slowly back more rich until the shake goes away. Go two flats (1/3 turn) more rich, and you're done. If you want to fine tune from there it's on to the lift-the-button technique.
When I run my MGA up Pikes Peak from 8,500 to 14,110 feet, it runs well about two full turns more lean than at sea level. Bear in mind you have much less air up there, so expect it to run like low compression and half throttle. Catch a lower gear if needed going up hills.