You are welcome. I will send you some photos of one recently done. I don't put extra creases in the cover, but I do attempt to pursuade the factory creases, by bending them back and forth. I do the first bend with the aid of a straight-edge on a flat surface, to make sure it folds crisply in the proper location. I have purchased them from LMC Truck in Lenexa, KS www.lmctruck.com and Classic Parts in Riverside, MO www.classicparts, since both suppliers are within 20 minutes of my shop and I don't have to pay shipping. You might also try:

www.truckandcarshop.com
www.brotherstrucks.com
www.bowtiebits.com
www.oldchevytrucks.com

I think most of them come from the same manufacturer, but I am not certain.

I strongly suggest removing the seat to remove or install a cardboard tank cover. If you have carpet, the wood block trick to push in the bottom is a must.