Distributor advance springs

I’m on my break at work right now and I did find this in my basic Haynes manual so I’ll try taking the distributors I have apart when I get back home this evening. This diagram certainly makes it look as easy as Rusty says.
The snap ring is a royal PIA. The roll pin is a minor PIA until you get experience with them.
Make sure you note which way the reluctor is installed.
Be careful not to use force on the nylon drive gear.

I'd only disassemble one if its hanging up or needs repair.
You can peek though the top plates and see the springs and weights.

This is for smallblock but same idea

Also, based on the valves both being closed when the timing mark is at 0°, everything seems to agree as far as valvetrain timing goes.
both valves closed and the piston at the top, then its fine.

No, the block is an older block. It’s orange. But newer parts have been added to it like a blue valve cover and intake manifold, and a blue oil pan. But the block itself is older.
Well then who knows what it has. You can see here the EGR systems and OSAC in '74. That should help you recognize what does what.
There's no vacuum amplifier for the OSAC, so I think it was for EGR. The EGR valve with no vacuum to it, should block it the exhaust gas - and if so, then the only adjustment to timing needed might be a little less vacuum advance. Bottom line is the exhaust needs to be blocked off.

If there is a snorkel vacuum door(s) make sure it(they) operate or are wired open to outside air...

My timing light is one I got from a thrift store for $3 lol so it works but the manual says it’s circa like 1984 or something like that so it’s just a light. No additional features. Will it still work? I’ve marked the timing mark on the balancer with a paint marker to make it much more visible
If it works, then that and a tachometer will get you started.