Help needed! Best cooking radiator for 67 Dart

Thanks all! Ordered a Cold Case from Summit. Will arrive this morning. Now the question is, what to run in it? 50/50, or distilled water with some thermal cure in it?
If you are in a year round warm climate, you can go down to 30/70 distilled. It will run a little cooler. Just make sure you use any brand that is green. No red.