Is your building to be used as a garage for the truck or primarily used for a workshop?
For a workshop, I would go with the 20x20. The extra width compared to an 18’and 16’ foot width would be more convenient to move around. You can always work on the vehicle front end or back end in milder weather by pulling the vehicle partly outside through end doors if necessary.
Sorry I don’t have the exact 102 dimension handy but, it would be about 204” in total length with a 125.5” wheel base assuming an 87” bed for this series. The width is appximately 74”.
The 18x22 would be good compromise if storing the truck. From my experience in small shops I had always wanted a couple more feet of width over length.
Can you design a cantilever roof overhang on each end (or the sides for open air storage) to increase the roof length?
The internet has lots of information for small shop designs. There are lots of creative shop designs and ideas that have been built to address small shop needs. Check out woodworker websites like Fine Woodworking or woodweb. Although woodworking sites, there are forums specifically for small shop designs from people who were faced with zoning or code restrictions too.
Last edited by tom moore; Sat Mar 23 2019 10:58 PM.