Unfortunately there isn't a direct way to do that. You could write some code that exports your 4.1 blogs in some format, e.g. Excel file and then read this file in your 4.3 project. Or you could write some code in your 4.3 project that connects to the RSS feed of your 4.1 project and imports the blog and blogs items. As I said, unfortunately there are no built-in means to do this out of the box.
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