Vetteworks
http://www.vetteworksonline.net/cata...products_id=89 makes just the weld on ring and it's only around $60, but you HAVE to have room at the top of the tank, don't think it will work on a 67-72 truck without recessing it.
Here's what I'm doing to mine, not finished yet, but I've done it in the past with good results.
