Your wiring may be similar to what I have with my '93 truck. I wired the speedo directly to the PCM red connector pin 50. I have a '99 harness so you probably want to double check to see if it is the same on your harness. According to LT1swap.com., your pcm pinouts should be similar. You should have a dark green/white wire at pin 50 on the green pcm connector. That wire is the 4K output wire. That controls the speedo.
According to my '93 wiring diagram, the instrument cluster plug has a light blue/black wire in the S position of the plug. That is the speedo wire. Just cut the wire and solder the wire from your new pcm to the end of the wire so as to reuse the little connector in the plug. Your speed should now work.
Good luck.
Last edited by Mickeymotormount; 02-03-2013 at 04:53 PM.
'93 Chevy 1500 4X4 ECLB with a '99 Silverado LQ4 6.0 and '99 Escalade 4L60E. SOLD IT!!
New toy: 2001 2500 HD 4X4 Extended Cab Long Bed
John