Wow, great job. I wish I had tried that tank. It looks to be the same as the Blazer kit I bought but on my 3/4 ton 4x4 it required some brackets be welded in. Also the tank straps would only fit on one side. Your frame appears to be much different so I will assume it's the difference between the 3/4 and 1/2 ton.
I haven't figured out how I was going to make the filler line but like your idea. I don't have a short bed so the plan was to come up in the wheel well as you did, just will be on the inside of the bed. Here are some pics of the install. Not sure if they will work...
http://i193.photobucket.com/albums/z269/Yroundriden/65%20GMC/20150104_172627.jpg
