In my opinion there is no reason to relocate or replace the core support. It is a whole lot of effort and expense with little or no gain. If you were able to find a V-8 core support you would still need the top cover plate which is different from the 6 cyl panel.
I did my conversion 15 years ago. I installed a 350 engine with the long water pump, a 3/4" WP spacer, a fan clutch, and a 6 blade fan. It puts the front of the blade about 2 1/2" from the radiator. I have had no cooling problems with this configuration.
However, using the short pump which is standard on a 327 it would probably be necessary to use a fan shroud. If you were planning on using an auto trans it would probably be a good idea to use a shroud in both instances.
Fred
