early 99 dont like its turbos please help

[hazard]

I'm working on my grandpas early 99 f250 and the turbo is pushing oil out the exhaust, the turbo that's on it was a rebuilt one he bought last year because the orignal was doing the same thing, well now that I have to replace the turbo again I would like to get a better turbo that isn't going to fail. What aftermarket or remanufactured turbo should I go with? The truck is stock with auto tranny and don't need anything wild but a more performance based turbo would be nice the truck is kind of a pooch, if I could liven it up with a different charger I would like to thanks.