What is the TBC suffix codeon small block Chevy?

With only that info it could be,

1970, 350ci, 255 HP, 4 bbls, K10 & K20, C10 to 3500, standard 3 spd or a/t,

or

1979, 350ci, 165 HP, 4 bbls, C10 to 2500, conv. cab, manual trans, fed.