I did the exact same job in my 76 HJ van. Donor car was a HZ Statesman. The only thing missing from the Satesman A/C was the compressor.
Mind you this is a Chev motor in the van and may be different where your alternator goes and other gear. But it will give you an idea.
Had to do a fiddle with some of the wiring harness to incorporate more electrics as there was not much there in the basic Kingswood van.
But that was no big deal as I just used the wiring harness from the Statesman. There was a difference between the wiring block that attaches to the firewall.
I moved these parts from the Satesman to the pano:-
Dash controls, under-dash piping, blocked the drivers vent, transposed vacuum tubes to back of controle module.
A/C -heater box went onto firewall when motor was out. Because the hoses and dryer were left opened for god knows how long a clean out with white spirit was not done, these were all replaced.
Cannot remember if we re-used condensor or if I got a new one.
Make sure you have enough grooves on your harmonic balancer to take the A/C compressor belt if you already have power steering along with alternator.
Now the kicker, I used a compressor from a 6 cylinder VL Holden Calais. I made the bracket from 8mm plate that bolted back along the manifold bolts and slightly around the front of the motor.
Works a charm.