You could try contacting Greg at FTRS
http://www.ftrs.com.au
they probably have the original equipment for making honeycomb radiators.
He will probably tell you just to buy a new one instead of using old tanks.
I thought with a honeycomb radiator you just plug the hex hole like the bees do and carry on?
There's Aussie Desert Coolers for re-coring. They said theirs cool 30% better than original. Don't know how they turn out.
Mine was re-cored years ago, bought second hand, doesn't fit the shell too well.
A new core with lots of fins should block the view of the tubes ...