I purchased a 64-65 Ford Falcon 4-Core from Chanpion (polished) for our 64 Valiant /6 408" conversion and it fits awesome, just slid it to the passenger side opening and made a small filler panel for the drivers side. I centered up perfectly this way and I run a six blade 15" fan....has 1" clearance with no fan spacer and is rated to 1000 hp.
Have some tweaking to do to the filler panel to clean it up like welding it in rather than the bolts and it should look more stock.
Plans also including fabbing up a polished aluminum .090 radiator shroud.