Mildon oil pan & pickup

I'm working on a 440. I bought the Milodon oil pan 30761, and also purchased the pickup tube 18660. I'm having problems installing the pick up tube. It seems the outer diameter is larger than the factory one by a few thousands of an inch. I'm at a point, to where it it's starting to gall the threads. Has anyone else had a problem? This is the factory 3/8 opening.

I haven't used the 3/8" pickup, but on the 1/2" pickup I tapped the block a bit deeper, and ran a pipe die over the pickup tube threads so I could get it in more than the two threads it originall went. The tap and dies are not hard to find, but not cheap either.

thanks, I was kicking around that idea. Just seemed odd that I would have to do that.