[TxMt] Importing Markdown posts to WordPress

[Dr. Drang]

I apologize for being off-topic, but I think there's more expertise on
this list than I'll find elsewhere.

I'm thinking about moving my blog from Movable Type 3.2 to WordPress.
As a test, I've set up a local WP installation and imported my old
posts--all of which are written in Markdown. They look awful,
primarily because the blocks of source code in many of my posts are
not being imported properly. Here is what I've done:

1. Exported the MT 3.2 posts using MT's builtin export command.
2. Installed WP and the PHP-MarkdownExtra plugin. Activated the plugin.
3. Imported into WP the text file that came out of the MT export process.

The biggest problem seems to be that WP isn't recognizing the Markdown
formatting of the exported posts. What should be enclosed by
<pre><code>...</code></pre> are enclosed by simple paragraph tags
instead.

Has anyone here experienced and solved this problem?

-- 
Dr. Drang