[Mart]

I've never done it but I believe people here have said they have done it. I think people say it is better to pull the tube out. It looks like it is threaded but they are not threads, just a series of circular marks, probably to provide a high spot at each part where it fits the block. You could pull the good pipe from the bad block as a test. It might be possible to thread a tap into the pipe and use a bolt as a puller. Or maybe drill a hole in the pipe in a place that is easy to access, insert a bolt from the end and weld it in through the hole. Once fitted in then new block the weld could be drilled out and the hole welded up.
Like I said, I've never done it but wanted to share some thoughts. Hopefully someone with direct experience will speak up.
Mart.