In 1972, Ford retared the camshaft timing by way of advancing the crankshaft...as you are noticing with your timing chain marks. Good observation by you!
The confusion that a lot of people don't realize is that some aftermarket double rollers timing chains are available as a 72-up chain & gear set
(Cloyes, for example, offer's a pre-72 & post 72 double roller chain). This would mean that where the round marker is 0* on the pre-72 version is actually 4* retard on the post-72 motors & post '72 style aftermarket chains.
Therefore, since your "0" setting on your current triming chain is advancing the crankshaft, it's obvious that you have a performance double roller chain that was created to 1972-up chain specs.
In your case, the way to correct your crank/cam position back to "straight up" specification is to simply install at the triangle (pointed keyway) in order to advance the cam back to 0* with the post '72 timing chain set. In other words, try a different keyway on the crank gear that will reposition the cam and crank keyways back into perfect alignment.
Alternately stated: Whichever timing set you have, the mark directly above the keyway is the true 0* (pre-72) cam timing setting (unlike the other two marks on the gear which are slightly offset from their respective keyways) regardless of which chain set you have (pre or post 1972).
So select the keyway that has the icon directly above the keyway (not slightly offset to one side of the keyway or the other). Also, the peak of the tooth on the crank gear will also be in direct alignment with the keyway and the keyway marking that is directly above the keyway. THIS IS PRE-1972 STRAIGHT UP. To verify after installation, both cam and crank keys should be at preciesly 12 o'clock when #1 piston is set to TDC.