This Ebay auction shows the back of 2 x HQ U21 guages:

http://www.ebay.com.au/itm/holden-hq...9#ht_83wt_1170

Shows the 120mph/200kM/h speedo has picking code QA, and the tacho has QM. Clock is QL.

HQ broadcast sheet for a Sandman shows QM for the tacho and QX for the 140mph/225kM/h speedo.

Can anyone add any more codes?

The codes I have off the HQ XX7 broadcast sheet are (left to right looking at them from the front): QW, QM, QK, QX, RD.

Is the fuel guage in the right hand one? If it is this will explain the RD code, muct have changed when guage went from thermal to magnetic sender.