I say anything beats building new ones. Once they're off the plane, there's almost no area that can't be reached by cutting into the rear baffle. I'm not saying that'll be required, but it is an option that would allow you to reach almost anywhere in there to reseal.
If all else fails you might want to contact Evan Johnson to have him build you a new tank. <[email protected]> I have seen his and they are beautiful workmanship. He will put in anything that you want for senders and pickup. George