For a long time I actually wanted to write about this. From several experiments that I have carried out, it has been proven that it is possible to convert a Tumblr theme so that it can be used as a classic Blogger theme.
Why convert? The newest Blogger templates are quite modern already!
I have a few of reasons for this question. First, Tumblr has a variety of interesting themes, both official (uploaded in Theme Garden) and unofficial in the form of bits of code uploaded to Pastebin and the like. I admit that most of the themes there are quite pretty and advanced for today's blogging usage.
Second, the Blogger's new template customization is limited, and it's not much different from the Blogger's old customization. I would rather create my own theme from scratch as good as I can. Apart from that, I also miss the glory days of Blogskins, and there is still a residual feeling of nostalgia that drives me to recreate themes in the style of Blogskins.
So, I say it again: it's possible to convert a Tumblr theme to be usable in Blogger, even though it would not reach 100% accuracy to the original because of the fundamental difference between those two blog platforms despite the codes' equivalents here and there. Understanding HTML, CSS, Tumblr and classic Blogger coding is a must, of course.
Next time, I will tell the basics of conversion somewhere.