jagarang, that is one sweet looking block!! Would you consider using an original waterneck and then painting it grey or block-blue? I think it would look fine, and preserve your paint scheme. The original waternecks can be found, though maybe a bit chipped. You know "Jagar" is German for HUNTER, though sometimes spelled slightly different.
'68 428 HO M3 Monster, 4-on-the-floor! Need I say more?