Dipstick tube install?

Thanks dusterdon, I thought about opening it up some but decided against it. The o-ring is a good modern touch, (I may use that). I talked to an old mechanic friend of mine today and he suggested putting the tube in the freezer for a night. Just before I`m ready to install the tube ,heat the area on the block with a heat gun, pull the tube from the freezer, and as fast as possible drive the tube in. This is the old-timers method and supposed to work. Last time I installed one I got it in by just hammering it in. It was ugly by the time I got it bottomed out and I thought it would probably leak but it didn`t. I wonder how the factory did it, you can`t even see a mark on the tubes where they installed them?