I think it’s a lost cause and you should give up so I can take that sweet truck off your hands
Yes, your distributor should have 24 degrees….was just trying to verify. Keep your total timing at 36, it should run very well there. Yes, you can plug your vac advance into the manifold vac port on the carb to see how much advance it provides. It should have no more than 10-15 degrees in it and be plugged in to manifold vac for it to work right. Another possibility, did you add the HEI and are you using the original power wire? The stock power wire has a resistor in it and won’t give the HEI the full 12 volts it needs. You can de-pin the wire from the harness and replace it with an un-resisted power wire.
Glad you kept the manual; it has lots of helpful info. Get the 1487 calibration kit, and together with the manual, you’ll have everything you need to set it up correctly.
Geezer is correct on the pressure gauge. The heat under the hood doesn’t agree with the liquid filled gauges and makes them read incorrectly. Maybe your Delco inline filter is making the fuel pump work a bit harder, reducing pressure? He’s also correct on your timing numbers too. I let that go since your total timing of 36 is more important than the initial.
I agree with HO455, make sure your ignition system is good to go, then move on to the carb. Test the distributor to make sure you didn’t get a bad unit. It happens.