Nothing wrong with having a radiator shop boil out & solder repair the leak. A new tank is not really necessary unless you have it boiled out & chunks of the skin of the tank are coming apart, then replace it. If the tank needs to be replaced, your radiator shop will advise you of the need. I am not sure why you mentioned POR15, is it capable of sealing a gas tank leak? If that is why you mentioned it, I think you are putting your life in extreme danger, when it comes to a fuel leak OF ANY KIND in a gas tank, have it repaired professionally.
It is EXTREMELY dangerous especially if you drain the tank yourself, drop it & try soldering it yourself, YOUR TANK IS FULL OF FUMES!
You may also want to consider replacing your gas gauge sending unit, there only a couple of bucks, if you drop your tank, now is the time to do it.
Frame off red 71 Chevelle SS496 Convertible with white stripes, top & interior loaded with factory options: TH400, cowl induction, power windows, locks, cruise, tilt, top, trunk, 12 bolt 373 posi, A/C, AM-FM 8 track, power drivers bucket seat, mirror map light, trunk, hood, glove box lights, on the wheel GM air pressure gauges, Delco Jac Pac 175 (under hood vacuum powered air compressor) with under dash Delco air pressure controller/regulator, complete with Jac Pac 175 air shocks.
1952 Chevrolet 4 door Deluxe Sedan with a 216.5ci in line 6 with the last RAJO (RAcing JOe) Power Cylinder Head designed by grandfather in the 1940's. Joe designed, built & sold all over the world performance heads during the 20's, 30's & 40's starting with the model T Ford. Joe drove in the FIRST INDY 500 in 1911 as car # 8.
Watch for my SS496 Chevelle as a pace car at Indy in 2011 (100 years after Grandpa Joe) IF THEY WILL LET ME !