I never liked the idea of using a spacer that I had to supply and center myself. I want it to be lightweight, balanced, and symetrical, I'm just weird like that.

I use the rear wheels with the spacer from two rears.

I have done two full size wheelset mods this way, one with KIT Racer wheels, and one with Zip Zap wheels (No pics yet).

This is a mixed blessing.

Yes the longer spacers hold the wheels out to where they don't hit when turning, but the wheels also have a wider stance.
I widedned one of my KIT Racer rears, and I will be building out my Zip Zaps rear as soon as my MS Gear and Wheel Tuning Kit arrives. The ZZ rear is getting the 8.25:1 gearset.
I am using old non-standard drive gears for spacers with gel super glue holding it all together.

You will also need longer custom pins for these wheels, but I had KIT racer axles to cut, I realize not everyone has these.
I also realize not everyone has the option to build out rears, but I like the resulting fatter look, and it makes the fullsize wheelset mod easier for me, and lets me not be neurotic about the balanced performance of my FS front wheels.