B2 of course! I have begun some work on adding my own personal touches to the module as well, and you can find the first installment here:
http://peoplethemwithmonsters.blogspot. ... obold.htmlReally, there are a billion different options available for what you are looking for. Be careful though. If you are trying to sell your players on old school gaming, much of the stuff out there is location-based and minimal when it comes to detail, and requires a strong DM with good improvisational skills to really be engaging.
If you want something with a built-in story and all that kind of thing, another good option might be to get this free module from Paizo:
Hollow's Last Hopeand just use LL monster stat blocks and such. For me it's easy to convert on the fly since I'm familiar with both systems, but for some it might be viewed as too cumbersome.
It really depends on what kind of expectations your group has. For instance, my group loves tactical combat, so even when we play a B/X-style game, we use minis and add a few 3.5-type rules to the combats.
Hope that was at least somewhat helpful.