Do freeze plugs work as they should???

Yeah i had this problem with my ole 318 in my 67 Dart about 3 years ago. I had water in it that summer and never filled it back up with anit freeze. That winter it Froze up but didn't pop a freeze plug out at that time. About a week or 2 later i had to put 2 freeze plugs in to stop it from leaking on each side. Car ran fine for about 2 years after that, then one day it just started running hot and losseing water. I would fill it back up and 2 days later it would be low again. Finally it got to the point where if I ride down the street it was hot and low on water with in a few mins. Now last week i jumped in it for a quick to the end of the street and back joy ride and when got back i decided to check the oil and what did i see. Milk shake nice lil vanila milk shake. Ok get this i just pulled the 318 out Wednesday and found that the block has 3 cracks, one on the passenger side and 2 on the driver side. Luck me I had already plan on replacein the 318 with the 360 I just got from the machine shop yesterday.