Looking for the wiring match-up to replace my existing thermostat 51H4301 to a Honeywell RTH7600 unit. My outside unit HP21-511-4P and the inside unit is CB19-51-3P-TXV.

The current wiring for the thermostat is:
O
G
C
R
T
W1 - two tied together on one screw
Y1
Y2

Can anyone help?

If you can give us the wire match up (color)of the old thermostat we can walk you through it. Or check out.customer.honeywell.com/Honeywell/getliterature.axd?LiteratureID

The wire match up on the old thermostat is:

O - Orange
G - Light green
C- Green
R - Red
T - Brown
W1 - a Red and a White
Y1 - Yellow
Y2 - Black

Does that help?

All should match up the same way. You can tape or cap off the brown wire "T" it is used for a outside thermostat. Set your new thermostat up for heatpump 2 stage coolng 3 stage heat.