Best coolant for our 60-70's Mopars?

I might have missed it but has anyone talked about how you have to get all of the water out of the system for Evans to really work? Also, what are you guys doing when you go to the track? You would have to dump the Evans stuff, try to catch all of it, then fill with water and hope you get all of the water back out before putting Evans back in. I was looking at Evans coolant for my Ram SRT-10 which is a alum block and heads but having to be 100% sure I got all the water out or else I would damage my engine stopped me.