[Spridgets] Metalurgical bearing type question

[WeslakeMonza1330 at aol.com]

Hi list,
 
I have an oilite bush in a suspension component where I'd rather use a  
polyurethane bush.  I can't get a poly bush in the right size and it seems  
more awkward to file than metal.
 
The oilite bush appears to have a relatively short life as nothing spins or 
 turns in it and it's subject to impact loading (as you'd expect in  
suspension).
 
I was tempted to have some Phospher bronze bushes made up but it seems that 
 apart from being able to hopefully have a slightly tighter tolerance 
(maybe a  couple of thou') there's not much to be gained.
 
So, what metal should I be looking for to have bearings made from?  Am  I 
correct in thinking that Brass being an alloy of Copper and Zinc is harder  
than Bronze which is an alloy of Copper and Tin?
 
I'm guess that the loading will be such that Nylatron or some other hard  
plastic simply won't be strong enough?
 
Regards
 
 
Weslake-Monza 1330