I've got these on mine, putting quite a bit of power through them, no problems, although I'm using ARP studsI can recomend ezaccessory.com as well used them great service and prices
FLETCH
looks like: damn, i miss calculated the narrowing of the axle and fooked up now im going to fix that with a poorly and cheap spacer. thereifixedit
Ah, I see that now you've mentioned it. Rear bolt on cap and the spacer. Makes sense now!Everyone seems to be assuming that that is some cotton reel shaped spacer, I doubt it.
Looks like the centre cap of the wheel with a small cast spacer that has snapped below it. Overtightening the nuts causes this.