here's how I did it.
however, the 67framw rails are narower, so a little trimming may be needed, but nohting major.
http://www.geocities.com/caddyoneton/
Also, a couple threads on the topic. This firts one is mega long, scan through and get the real good info.
http://67-72chevytrucks.com/vboard/s...ad.php?t=20020
http://67-72chevytrucks.com/vboard/s...d.php?t=194481