68 Cuda Max radiator size ?

Your set up is much like mine. I bought one of Mancini`s custom made 22" aluminum radiators and it`s been quite adequate. The core is probably 3" thick. Fan clearance is tight but I`ve never had any issues with overheating, even during Va. summers. I`ve seen guys running the 26 " radiators in the 22" spots without an issue. It may not get the full air flow but the added capacity is beneficial.