I went through this, no need to dimple or spacers with the CP50014 box. They have the whole conversion kit if you need one. I had to order a ps pump mount from ebay cause i have a 292. Feel free to PM if you have any questions
http://67-72chevytrucks.com/vboard/s...d.php?t=729738
The second page has a pic of the box mounted to the frame with no dimpling