Speedo's fine, the electrical pulse thingy for electronic speedo is attached just like the speedo wire, unscrew one and plug in the other.
Both aw4's have a computer, the same AFAIK. But the old AW4 had a "comfort" switch which the HO (1991+) don't have, so something is different with the wiring, and probably the computer as well. Now the interesting question is - do the old AW4 interface with the engine harness the same way as the new? I know the AW4 reads the TPS among other things. I'm not sure about this.