HUD dash with gts swap

[kidslice]

Ok so I'm at my knowledge limit here with this, so I'm asking around and searching online for answers. I had a 1991 240se and now have a 1990 with a RB25det GTS engine swap.I took the HUD dash out and windshield from the 91 and swapped it over to the 90.I can get my RPM gauge figured out no problem.But how do I get the HUD on the dash to read out my speed .As of now every thing werks fine in the cluster cept the HUD speedo and the digital speedo are not reading.Every thing on the dash werks fine just don't know how to wire up the HUD and digi speedo.Any ideas?????????????Thanx!