Texture paths are a bit different in BFheroes then it is in BF2. 
BFhereos does not separate vehicles into separate subfolders according to category like with all other BF games. Thus when you put a BF2 vehicle into Bfheroes, it's easiest to just create the folders as BF2 had them.
For example, BF2 had tanks and jeeps here:
Objects/Vehicles/Land/
But BFheroes vehicles have this path for all vehicles:
Objects/Vehicles/
Thus just create the land folder (and air/sea folders if you do any aircraft and boats) and put your BF2 vehicles in them.
EDIT:
Did a test port by porting the Tunguska from BF2 into BFHeroes. And I was correct in replicating the folder structure. THere is a couple small areas missing textures. Most likely because the vehicle uses a few common shared textures that are probably located in the common subfolder found at the root of the vehicles sub folder. Thus copying those too and preserving their location the same way as the main vehicle should allow for all the textures to work.
Though additional changes are needed if you want the HUD for the vehicle to appear correctly and for the camera position which is all jacked up when ported to BFheroes. :P
Fastest vehicle port ever for me. Took me all of 30 seconds to get the files copied over and the vehicle worked on the first attempt. 
Video coming soon. Uploading it now.
EDIT:
Here's the video: (click image to view)
TunguskaInBFheroes (photobucket)
I used photobucket since this was a small project.
Thanks for the ammo count adjustment suggestion! The last time I tried converting BF2 vehicles to BFH resulted in a CTD. Now I know why.
, because i dont want to exceed my bandwith 
and the barrel is in the wrong place. 
