You could pop across the line to Ricks Ring and Pinion. You're definately close enough Everett, WA

I have heard the Yukon gears are a little nicer for drivers as the richmond gears like to make a little more noise...

You will need the spacer if you use your existing carrier once you go over 3.23 or 3.36 i can't remember...

I have been told to be careful with the used posi's as typically they are the cone type and after 30+ years are usually getting close to the end of their lifes