Compression Stroke after verifying TDC
First you back up and start over with a bar on the crank. When she feels the compression air coming , STOP. the piston is on the way up, and soon coming to TDC. You have to physically stick something in the hole to feel where the piston is. That something must not be made of anything that can break or lose material in the chamber I use a screwdriver with a really long shank on it. Do not use a bump-starter. On the compression stroke, you don't have valves in there to worry about. I put the tip of the screwdriver on top of the piston then lift up on the handle. As the piston rises, it will cause the handle to go down. Make small adjustments on the crank atta time, and pull the screwdriver out a lil, each time; because as the piston comes up, sooner or later it is gonna want to jam the screwdriver in there. When the piston gets to the top, there will be several degrees where nothing seems to be happening; just shoot for the mid point.
Now go look at your balancer.
You say you have a drivers side timing tab, and I can see that. The question is do you also have the matching balancer for it? By your piston stop work it would seem so, so the balancer mark should be there.
But if it's not, it may be on the passenger side, go look.
If it is then you will have to redo the piston-stop business and make a new TDC mark.
The thing is; once exact TDC is established, you can make match-marks anywhere you want to that is convenient. I have made them while laying on my back under the car cuz that was the only part of the balancer I could see. And I have on certain 70s vans, removed the doghouse, and drilled a hole in the bellhouse and made matchmarks there. You can put them anywhere. The factory chose one place up to 1969, and when the following year, they introduced a different aluminum waterpump, they had to move the timing tab to the other side.
I can see that you have the 70and up aluminum waterpump, and the 70 and up timing cover..... but from the installed pics, it is impossible to tell if you have the right 70and up balancer.
So if the mark doesn't show up, the simple answer is to make new marks. This will work just fine if the balancer is, or has been, matched to the reciprocating parts .
Since you have already done the piston-stop TDC finding method once, second time round is easy.
However, I agree something is odd; I does not matter whether you find TDC with the piston on compression or on exhaust; TDC is TDC. So that begs the question; if your mark doesn't come up on #1 DC compression then you have only three answers; #1, you were not on #1 cylinder, or #2 it was not at TDC, or #3, it moved after you marked it.
Happy hunting
BTW nice camera work
