About matching parts, Bricklink contains useful data, placed at the bottom of part description. Eg. here http://www.bricklink.com/catalogItem.asp?P=6870 we learn that 6859 matches 6870 part.
You can see the database here: http://www.bricklink.com/catalogRel.asp
SR3D builder has a tire matching tool.
You can see the database here: http://www.bricklink.com/catalogRel.asp
SR3D builder has a tire matching tool.