We work with Delrin daily. It's chemically resistant, slick, durable, but sucks at impact resistance. In a leaf spring it might be ok, but it could shatter on a hard hit.
It's also temperature sensitive. Low temperatures (under about 40F) it turns even more brittle.
As far as plastics go, the only stuff I'd use after a large number of failed bushing designs is this stuff called Vesconite. It's tough, impact resistant, machinable, is self lubing, doesn't abrade easily, gives a decent amount of friction in a press-fit situation. It's expensive and hard to find, though.
