"TBO" is a brand name. It stands for "Touhoku Bikkuri Oojisan":D
This is the TBO Front Bumper...
About the SR20 swap, I just love how the SR20 almost entirely sits behind the front struts, almost like an S2000... when you get to be my age (28), you start worrying about weight distribution and other stuff like that. Also, if you buy right, you can get a much more late model SR20 than the origional RB20, and they've got practically the same power, so it's not like your going backwards.