Thanks for the suggestions. I left them with my local engineer who was going to try lathe or grind or (most likely) turn up new ones.
The bogie is almost finished, the race is on Saturday and I'll need to fit the bearings, bed in the brakes and get a handle on the handling before then! Had a drive up & down the course this evening and it looks straightforward unless they put chicanes in.
It shouldn't hurt too much!