[RichardJ]

I see you don't have all the AC hoses connected yet. Did you consider mounting the compressor on the pass side of the head so that you could install power steering?

Of all the things I have done to my truck, PS, AC and taller rear gears have provided the most significant, night/day improvement to the truck.
Those three things make huge difference in how much you will enjoy the drive, what you smell like when you get there and how long it takes to get there. Wrestling a manual steering truck with a wagon wheel size steering wheel into a parking spot is no fun.

Did you see or consider the AC bracket Vintage Air sells? I made my own bracket, but it is very similar to the one they sell. They say theirs will only fit above the stock distributor, which is fine for your Pertronix.
Mine will not fit with a regular HEI distributor either, but does fit with the six cyl, external coil HEI.

GM started using the HEI in '75 with the recommendation of .065" plug gap. By '80 they were recommending .045" and by the late '80s, most applications called for .035" gaps.

With an HEI, I use .035" , get 15 mpg hwy, drive 75 mph all day in a cold cab, and don't know what color the AC plugs are because I haven't looked at them in a couple of years.

Be sure and use a parallel flow condenser.

I'd get rid of the long fan extension. Without a shroud, the extension will not increase air flow. The only thing I would expect from the extension is possibly greater wear on the water pump bearings.
I am also using the original 4-blade fan with an electric pusher fan in front of condenser. No heat problems under any conditions.

A PCV system must have a means for clean, fresh air to enter the crankcase and an exit for some blow-by during WOT. Most of the original valve covers have a side hole for hose to the air cleaner, but at minimum, a breather fill cap will work. Generally a much larger air cleaner will provide far more air flow and with considerably longer replacement or cleaning intervals.