I have a 2001 Dodge CTD and want to run B100.  I want to know if there are any modifications that I need to do the engine to do so.  It seems like no one really knows the answer to this question. 

you dont need to modify your engine in any way.  One thing you'll need to do is change your fuel filter more often until your fuel system is cleaned out.  So hone up on your fuel filter changing skills, its pretty easy and quick.  Filters are about 10-20 bucks and usually all you need is a crescent wrench and rags to change it.  Keep the filter with you in the truck.  When the filter starts to clog, you will notice your engine stumbling on acceleration.

My '01 has been running B100 four years. If you don't know how to change a fuel filter, learn how and install a fuel pressure gauge if you haven't already.

Make sure you know that the quality of the fuel is good, don't get it from someone that has just started making it. 

I'm new to BD so take this with a grain of salt. There are no NEEDED modifications but from what I've read you may want to change your fuel lines. Standard fuel lines break down over time.

Newer vehicles come equipped with fuel hoses that withstand high blends of biodiesel very well.  Even so, if your older fuel lines dissolve with biodiesel use, they will warn you by sweating or leaking.  I dont consider upgrading your fuel hoses a modification, only good maintenance.  In a 2001 vehicle, no need to worry about changing fuel hoses.