I needed a new radiator for our '66. Trying to find a serviceable radiator with the right part numbers and dates and the G2 designation for a 4 speed car is REALLY hard. I ended up going with a brand new aluminum radiator from Virginia Mustang while I search for a correct one knowing it may take months/years. I ordered the MaxCore radiator and it fits perfectly. If you do order a new radiator, ask about fitment of the fan shroud and also if you need to make an adjustment on a longer/shorter fan spacer based on the thickness of the radiator. Also, you will want to order Eastwood paint made especially for radiators. Ecklers is the best (only) source I could find for this paint right now.
In doing a lot of reading, the aluminum radiators are counter-intuitive in that a 2-row is better cooling than a 3-row because the tubes inside are so much larger. Here is a quote from the Virginia Mustang website description:
MAXCORE 1.25" Tubes - Innovative 2 Row Performance MAXCORE performance. If you say, "only 2 rows", you need to think again! The MAXCORE design utilizes huge 1.25" tubes for perfect flow and amazing cooling.
Here is a link to the '68 Big Block MaxCore radiator should you care to check into it:
https://www.virginiaclassicmustang.com/67-70-390-428-and-70-302-351C-Mustang-Aluminum-Radiator-Original-Equipment-Style-Bracket-Mount-2-Row-Performance-P482387.aspxIdeally though, someone may have a perfect OEM radiator you could use.
Jeff