This picture was borrowed from the HAMB (Hokey Ass Message Board).
To replace the timing set, typically all/most of your belt driven accessories need to come off. So, remove fan, crank pulleys, harmonic balancer, and most difficult with a SBC, the oil pan has to at least drop down a bit in the front, to remove the timing cover, as the oil pan seals to the timing cover. Once the oil pan is dropped and the timing cover removed, I would make sure that the engine is at top dead center of the compression stroke at the #1 cylinder.
So, prior to removing your harmonic balancer, pull your valve covers. Rotate your engine to align the timing mark on the balancer with "0" on your timing tab. From there, rotate the engine back and forth (easiest with all plugs removed), and either #1 or #6 rocker arms will begin moving within 10°-20°. When they both move reciprocally, that is called "teeter". You want #6 on "teeter". If #1 is on teeter, rotate the engine 360°, and verify that cylinder #6 is on teeter. This verifies that #1 is on TDC of compression stroke. You can accomplish the same thing by sealing the #1 spark plug hole with your finger/thumb, and rotating the engine clockwise from standing in front, looking at your engine, or counter clockwise from drivers seat. When air forces its way out, as you approach TDC, you are on compression stroke. That feels like a three handed job to me, so I pop valve covers and verify by lack of valve movement immediately before or after TDC, or by verifying that #6 is on teeter. This is also a good time to mechanically verify your TDC mark, by using a piston stop, but either myself or someone else can help with that when the time comes. The small gear goes on the crank snout. It's keyed, so can go on only one way. Put it on with the obvious dot facing out. At TDC, this dot should be in the 12 o'clock position. Hang the timing chain on the bigger cam gear (with dot facing out) and rotate the camshaft so that the little peg aligns with the fourth hole in the gear, and index the gear/chain so that this dot is at the 6 o'clock position, perfectly aligned above the 12 o'clock dot on the crank gear. You may have to play with indexing and rotate the cam a little to get it perfect, but it's not hard. Torque the three camshaft timing gear bolts (I like to use red loctite, AND the little $3 plates that have the tabs that you fold up, to prevent the bolts from backing out. Once that is verified to be perfect, clean the old gasket material off of the block and timing cover, and reinstall the timing cover with a fresh gasket. I use black RTV. A tiny bit on each side of the gasket. Then reverse the order that you took the rest apart and press the balancer back on with an actual balancer installer! You can rent/borrow these for free from auto parts house, with a refundable deposit. After you button it all back up, verify that you're still at TDC, and then I (personal preference) rotate the engine to 10°-12° advance. Then I pull the distributor cap, loosen distributor clamp just enough that you can rotate the distributor, and then rotate your distributor so that the rotor inside points right at (or at leading edge of first contact) the #1 plug wire terminal on the cap. All of my distributors have a mark etched into the body right under the center line of the #1 spark plug wire terminal, so that I can index them to the #1 terminal with the cap off. That will get your timing very close to dead on! Then, after you fire it up, check for leaks and get it up to temperature, you can dial the timing in as needed, typically around 12° at idle, 36° "all in".
Reference: photo borrowed from post of user "Steel Rebel", located at:
https://www.jalopyjournal.com/forum/...nging.1022260/