another 360/408 over heating

Dana67Dart
I should have mentioned it in the original post but my first drive was with a 50/50 coolant which had the coolant at around -20*. Before i did the 2nd drive I cut the coolant to about a +5* and thats when I added the water wetter.
Are your thoughts on shrouds because you restrict free flowing air while driving the car down the road? Thats the reason I cut the holes in the shroud but I havent gotten to drive it since I did that. As mentioned in the first response from Blind Squirrel that holes can cause issues I plan on putting some rubber flaps on the holes so when idling the holes will be closed forcing air to be drawn from the front.
As for the gas in the coolant my compression tester just arrived today and I also plan on doing a cylinder leakage test. Even tho I hate to believe the test of gas in the coolant the reality is that it tests positive and chances are that could very well be some if not all of my issues. I would just like to cover any and all other bases before tearing the heads off. I do have a set of aluminum performer heads ready to go on should I find the heads are the issue.
Rod