Campagnolo Record headset lightweight and 1" threaded. The name Record should tell you all you need to know - smooth bearings that will last years. It has a 26.4mm crown race of course.
English BSA threading but it will thread on to Italian threaded steerers without damaging them (TPI is the same but the italian thread pitch is different by 5 degrees not enough to make a difference).
Stack height 38.5mm