Biggest most massive 4 core rad for a 68 Barracuda?
Take your car with the rad that is in it, and go to a RADIATOR SHOP! Do not waste your money at a quick lube type shop that offer rad flushes. All they do is cut your heater line, install a "t" fitting and run a garden hose to it and "flush" your system.
Save your money on that and go for a good meal with the wife or girlfriend.
A real RADIATOR SHOP will do a reverse system power flush, which is compressed air and water and they will flush out your heater core, block and radiator the right way.
You may need a re-core on your radiator, a good RADIATOR SHOP will take care of your car and make it work! Ask around.
FYI- A radiator has a CORE, the CORE is made up of fins and ROWS of tubes, usually 1 - 4 ROWS.
So when your talking about a 4 CORE radiator your actually meaning a 1 CORE with 4 rows...