Here is one for the box, not sure if you had planed on new box sides:
http://67-72chevytrucks.com/vboard/s...d.php?t=509442
I plan on using this guide for my box along with the one LockDoc posted to convert my lwb into a swb. I would like to find a swb and just use it but there doesn't seem to be many around where I'm at.