All issues of Blackthorne's 3-D series are dually-titled and are indexed under their their individual titles. See the issue records here only for directions on where to find complete information on these issues.
There were two #49's published, Rambo III in 3-D #1 and Sad Sack 3-D #1. Issues 56, 68, 73 & 76-79 probably don't exist.