Call up the major companies that make aluminum rads. Griffin, Be Cool, maybe some local shops?
I would expect to pay anywhere between 300-600 for a quality unit.
I have a becool single core. I paid 250ish. Says it will cool 350 horse easily. I have two 1200 CFM proform fans and a 35 GPM proform electric pump.
That cooling setup worked for my 357(died, for other reasons
). I don't know exact power output but it was an alright motor. 10.5:1, comp 270H magnum, stock heads, weiand manifold.
I now have 307 till I can get a 383 built. It should very easily handle the 307 but I doubt it will be adequate for the 383, unless I build a really crappy 383!