Start by assembling the left and right sections to the middle section, wood, chrome surround strips, etc.
Carefully install the glove box interior pocket onto the back side of the dash.
Install the door and all the associated bits.
Install all the gauges and instruments, direction indicator assemblies, choke cable sleeve(get it good and tight) etc. to the dash assembly
Do not install the toggle switches or ignition switch to the dash yet, but do install the appropriate wiring to them and leave them hanging for now.
Have the heater assembly, air duct, hoses, etc. already installed in place.
Have the heater control panel and associated cables fastened to the heater assembly and hanging by the cables.
Hang the complete dash assembly, fitting the two outboard studs mounted to the back side of the left and right wood through their mounting brackets and the two upper corner screws of the centre panel fitted through their under dash bracket, and run the flat washers, lock washers and nuts on finger tight only for now.
Now, with the car completely void of interior, (also helps greatly to not have the steering wheel yet fitted) lie flat on your back under the driver's side and with a good light and wiring diagram handy, install the wiring harness to all these components.
Fit the heater control panel assembly in to the dash aperture from behind. Some cable routing and adjustments will be needed so everything fits "comfortably".
Fit each of the 4 switches and the ignition switch through the switch panel, offer up the chrome switch plate from the front and install the locking rings.
Install the oil pressure line to the back of the gauge, not forgetting the little leather sealing ring.
From the passenger's side, install the glove box interior liner support plate from bulkhead to bottom of liner.
Climb out and observe if the dash assembly needs to be centred from right to left. It's normal to have to shim washers between the end support brackets and the side bulkheads. Remember that the side kick panels also need to fit into this gap.