Leaking from the nipples where the vent mechanism attach to the front of the tank? Did you replace the rubber hoses there?
I would suspect a radiator shop that deals with gas tanks should be able to re-solder the nipples to get them leak-free again? Should not need to get a new tank for that, unless "the rot" is more advanced.
New tanks? Should be the same tank that normal C-body Chryslers use. Spectra is probably the only manufacturer of them. As other places use the same part number as Spectra, I suspect they are re-selling Spectra tanks at variable prices, so PRICE SHOP, including for "free shipping". Van's used to have the best prices, and such. Rock Auto CAN be a contender though.
IF your existing sending unit works, do NOT get a new sending unit, reuse the existing one! Do get new seals and such.
Edelbrock 800cfm carb? WHY?
Enjoy!
CBODY67