Had a pattern one on mine (bought from British Spares in NZ) for 5000 miles now and the build quality is pretty good. I went through two Smiths units in 23000 miles which, apparently, is not untypical. Make sure it's got a "grease" nipple that works so that you can give it a squirt of oil every 2K or so. A rebuilt Smiths unit, regularly oiled, would be the best choice, I agree.
Cheers
Nick