here is mortec's decoding

3914678....302.....68....2...Z-28 Camaro
3914678....327.....68....2
3914678....350.....68....2

could be ither 1, but a 302 would have DZ cast into the block. probably a 327, casting number is accurate for a '68 327 and that's what your told it was. have to be dumb luck to get a '68 350 with that casting number, just to trick sombody.