Here's a link to their info page for the 67-72 GM truck kits:
http://www.vintageair.com/67-72chevygmcpup.asp
I tried posting pics but they were huge when linked directly to their image. Go to the bottom of the page on the link above and click the pics. The evaporator is mounted under the dash, completely inside the cab behind the glove box. you'll lose most of the glove box because of this though.