I think you are asking which bodies and hands will go together? Is that with or without modification? I am going to limit my response to the major players as I see it. Medicom and Sideshow I will not comment on. There are also other bodies out there also. So, I will limit my response to ACE, Barracks SGT, Blue Box (BBi) G3.5, Hot Toys (HT), Toy Soldier (TS), Soldier Story.
ACE, Barracks SGT, BBi G3.5, TS, Soldier Story have interchangeable parts. Neck post and hands will work pretty much seamlessly. HT heads / neck post will work with ACE, Barracks SGT, BBi G3.5, TS, Soldier Story connectors. ACE, Barracks SGT, BBi G3.5, TS, Soldier Story hands will fit HT also but you have to use the HT peg hand connector. DML head will fit on ACE, Barracks SGT, BBi G3.5, TS, Soldier Story and HT bodies with a adapter offer by Transplanter Productions (Check Coltswold or Good Stuff to go). ACE, Barracks SGT, BBi G3.5, TS, Soldier Story hands / connector will work with a DML body. Feet are a different issue and modification is required for most figures. DML bodies are proprietary and parts are not interchangeable with much of anything. BBi G1.0 bodies heads / neck post have the same flexibility as the G3.5. Hands require modification of the connecting post (Generally shorting it).
Let me also say that the version of HT bodies I am referring to are the True Type 38 figures and perhaps the version before for performing hands and heads exchanges. HT changed their feet configuration with the introduction of True Type 38. If you can get a copy of Spec-Figures Volume 2 or 3 (Hobby Japan, Mook) that will help you a lot by providing pictures and workarounds. Beware, these manuals / books are all in japanese. Also check this site in the Custom Tips & Techniques section.