was driving car last week and noticed that when i let my 1970 cutlass oldsmobile 455 big block idle at rest it would slowy get up to 175-185ish,, when i decided to take it out on airline cruising at 65 mph eventually it got up to 210 and wasnt droping, you would think that the ram air going throuh radiator would cool it down? i have fan shroud on it with new flowkooler waterpump and new thermostatic fan clutch. im using 50/50 prestone antifreeze mix and the level is all the way to the top when engine is off, when i opened the cap up while started it droped at least 6-7 inches down. why is this duing this? is my radiator done with?(been sitting in attice for so many years).,.. dont know the condition of it, i have done a flush and not much crap came out,... is is a brass raditor.

my 70 cutlass
455 big block
flowkooler waterpump
thermo fan clutch
160 thermostat
16lbs radiator cab
okay so after this my question is do i go back with a brass 4 core radiator like before or go with an aluminum one?

brass/copper ones ive been looking at?
http://cgi.ebay.com/ebaymotors/Spect...item2eb68f8342

aluminum ones ive been looking at?
http://cgi.ebay.com/ebaymotors/Alumi...item588f56a67d

http://cgi.ebay.com/ebaymotors/Chevy...item1c1ea946f3

any ideas on what i should go with and what exactly are my problems? help is appriciated, thanks everyone!