Definitely, the .OBJ won't be linkable into Harbour. Clipper 5.2 was 16-bit, Harbour is 32 & 64.
Most likely, the .ASM will need to be modified, then compiled into a 32-bit .OBJ, then linked into the Harbour application.
Whenever I faced this problem in the past, I tried to rewrite the functionality of the .ASM or .C module into Harbour, even if there might be a performance difference.