when I load up GECK, and load data, it tells me I cant have multiple master files. However; I in the mod I'm trying to make I wanted to use objects from the different mods: specificly, I'm trying to make a ruined city and need parts from Lonesome Road and the GECK has already decided that my mod uses the base game and Honest Hearts.

Is there a way to get just the list of objects from the DLCs, without the maps and other data?

From Here: http://geck.gamesas.com/index.php?title=FAQ#How_do_I_load_multiple_masters_in_the_GECK.3F

How do I load multiple masters in the GECK?

To load multiple .esms in the GECK, you need to change this setting in the GECKCustom.ini file:

bAllowMultipleMasterLoads=1

Just note, there is a reason this is set to 0 initially, you want to be careful when designating multiple master files, mostly in choosing other mods as Masters. The DLCs will be OK to do this with.

Also, note, you might want to look into cleaning the DLCs with FNVEdit to remove the dirty edits so those references do not get propagated into your mod. The following is for cleaning Skyrim, but your doing the same thing in New Vegas, and it is even the same tool really, once you rename it

https://www.youtube.com/watch?v=fw3g_N1jcZQ