CraigM - I'm not 100% sure but I think I built my car without any spacer behind the trust. I ran the cone washers (((( I can't remember how many come in the kit - Origionally I designed the car with only 4pcs but I think they put in 6-8 for production (I can't remember). This may also be the reason my blades were ok. I may have ground the end of the diff screw a little shorter but I'll have to check to be sure...