I put needle bearings in my GT about 30 yrs. ago and have had no trouble with them [haven't really looked at them either!] I don't run it much anymore. But they have held their adjustment,unlike when running the bushings. To be fair I was running 50wt. when the bushings were wearing quickly and I think that is the reason as the oil took a while to be splashable into the little hole in the rocker. 20w50 seems to remedy that issue. I guess it depends on what you can find. I recall Guzzino.com had shafts and bushings available. The rollers are probably a std. bearing and I think you use 3 per shaft and a short spacer[old bushing sections] on the ends. It has been a long time since I did them.