Well I opted to use the POR-15 product instead of a new tank. My tank didn't actually leak and was in great shape on the outside for its age. Better than I can say for myself !!!! It seems to be working fine as I've had it full of fuel for a week now and no leaks.
After cleaning out by first putting in a gallon of new fuel, sloshing around, dumping into a container and straining the crud out this was done several times. Once the rinsing gas seemed to come out without much crud the tank was filled half way with hot water and some dishwashing detergent. Again some sloshing around, pour out and repeat several times until all looked clean. Next I dropped in a small length of chain like for a swing and turned the tank over and over several times, more hot water and detergent, remove the chain and dry out the tank with a heat gun.
Following the instructions with the POR-15 all went well and now back in the truck and seems to work great. A word of caution.........USE GLOVES, yes USE GLOVES. I did after getting some of the sealer on my hands but too late. NOTHING will remove that stuff as I tried everything in the garage and house from paint thinner to brillo pads. But if you are like me and prefer to not use gloves it will wear off in 3-4 days.
Good luck and thanks guys!