Found this in the GTS registry, doubtful it's a match.
I picked up my car around 1995 in south Florida, from a guy I knew that had it for awhile before that. Most likely the engine came from another Florida car.

LS27P9B413***: GTS#606: This is a One-of-58 built 1969 GTS 340 4 speed convertible! Located in Michigan, Mike C. is performing a rotisserie restoration on his rare convertible. The body is painted B5 Bright Blue with black convertible top, black interior, and black bumble bee stripe. This was all powered by a 340, 4 speed, and 3.55 gears.