The big challenge you'll have is generating enough CFM to cool that big block, pull fans work best and even better with a shroud. push fans are generally less effective. I've a 17" on mine rated at between 2500 and 3000 CFM it's in a full shroud so i'm hoping it's nearer the top figure. I would think you'll need 4000+ for a big block. Buy a good make too (like SPAL for instance) most cheap chinese stuff makes nowhere near its stated CFM.
This is one situation where size really does matter
both radiator and fan.