Two blogs with different themes but the same Loop?

Basically, I want to have two WordPress blogs, each with it’s own theme, but that runs off the same posts.

The reason behind this is I want one version that has all the extra WordPress add-ons like the title box, the footer, the navigation… All of it. But I also want a version of it without all those things that’s just the articles, but I’m not sure how to do that.

I’ve designed my theme (mostly) and put it in the themes folder with all the default themes and it works fine and does what I want, but if I set it as the default I lose all the other abilities of the other themes with all the extra stuff.

I’ve tried straight linking the index.php file but that didn’t work. Anyone know a way I can do this or another way if possible?