high speed overheating

The faster i go the hotter it gets. i have a 3 core 22inch copper replacement radiator in exultant shape fan shroud rubber air dam on hood and 340 engine half filled with hard block.I am told my radiator is adiquit but its still heating up on hot days over 60mph. would a high volume pump help. I am thinking only at low speed. looks to me like i need more radiator. dose the hard block make that much difference.I WOULD Appreciate some advice on a solution. THANKS.