I got mine from Mustangs Unlimited, new 3-core @ $129.00. There are even 4-cores available, but these L6's are made to run hotter for better combustion (180 to 200 degrees) I was told. They have different brands to choose from, I chose the cheaper one and have no problems. The temp runs @ 180 degrees with a 160 stat and in 95 degree weather while cruising at 2500 rpm. 50% antifreeze/water mixture. Good luck.
Kirk ' 73 bronco
ps. I rate the vendor above average.