What's the easiest way to do it? I know some people use washers and cut them so all you have to do is loosen the top bolt and slide them in but is there any chance of them sliding out like that? Are there any premade spacers that work better or have a lip on them?

Going from a 190/55 back to 180/55 is such a hugeee difference and I want something that's easy in/out for when swapping between street and track tires. Should I just consider a shock with adjustable ride height?

 

Take the shock mount nut off and remove stud from crossbar, put some washers on, re-attach shock to crossbar. As simple as it gets without getting an aftermarket shock.

 

True that, it's only one more nut.