bed mounting question

[gono]

Did a search on a different way to mount the bed on my 55' stepside but didn't find what I was looking for. The truck is notched in the rear but I'm still going to install the bed so it will be raised about 5-6". I was planning to use the extra space under the bed to mount the air tanks so using the original bed rails is out. Has anyone else run into this or remember a build thread they can point me to? Thanks.