I really have no clue how to do this. Any good videos you recommend?
it has a Muncie 420 with 4 on the floor.
Let me take a 50,000 foot crack at it... I am assuming your vacuum advance is hooked up to manifold vacuum, not ported vacuum (which is for smoggers).
The 1st thing I would do is find out what you currently have. There is no telling what is in your distributor; it looks like you have an aftermakret adjustable vacuum advance cannister. What's the condition of the points set? Maybe you have a points eliminator?
Get a timing tape and install it on the damper. Get a timing light and dwell meter. Maybe you know someone who has them and knows how to use them?
Unhook and plug vacuum advance hose. Note idle speed and read timing. This is your current base. Rev engine to get max advance; probably 4,000 or more depending on advance springs and weights. Expect anywhere from 28 to 36 degrees.
Distributer centrifugal advance is max - base. Exepct somewhere around 25 degrees. Note: This is engine crankshaft degrees; distributors run at half the crank speed and specs are listed in distributor degrees, which is half the crank value.
Let engine idle and hook back up vacuum advance source hose. Measure timing. This number - base is your current vacuum advance. It is also possible that there is no vacuum advance if your cannister is bad.
Now you know what you have. You need to decide what you want. For that small bore short stroke engine in a old pickup with today's gas, I would set max centrifugal advance at maybe 32* at 4,000 RPM with 8 to 10 degrees vacuum advance. Let idle timing fall where it may. It should be anywhere from 4 to 12*. You can go more agressive with rpm (lighter springs) and more lead (Chevy V8s like a lotta lead) to get a little more performance but watch out for ping and use premium.
Remember, you need vacuum advance at low load because lean mixtures need more lead to burn completely.
Beyond that you need to get more serious. I like to set base at highest manifold vacuum and max centrifugal around 34 to 36 on my 60's cars. And go real easy on vacuum advance because my BB Chevy and Oldsey, with their compression and iron heads will ping like crazy on crappy wanna be CA 91 Premium.
Good luck and have fun with it. I would enjoy that old truck.