Cooling question

Hey, this question is for a non-IT car, but how critical is it to retain the cooling outlet on the end of the head versus just block it off? I'm wondering in particular about a 1.6 8V engine but it could apply to other VW 4 cyl engines. I've seen high-horsepower prod and GT engines built both ways. I am guessing that there might be a temperature gradient through the head if some coolant flow is not retained on that end but that may not be true...

I think that on the early heads you can pull it all from the side of the head, and on the later 1.8 (also 1.7?) heads you can pull it all from the end of the head.

I know that on a friends prod car we pull it all from the side of the head and block off the end port on 1.5 and 1.6 prod motors that need a lot more cooling than they did stock.