Crank position. The crank position is a direct indicator of the piston's position, and when the spark plug fires (distributor rotor's angle) is more critically timed to the piston's position at various RPMs (before or after TDC, advance/retard etc)
Not saying the cam's position is not relevant, but when considering the distributor, you are essentially discussing spark timing and piston position.
The cam's orientation impacts the valves' positioning during the cycle and in terms of the distributor timing, would affect whether a valve was possibly still open at the time of a spark, or perhaps prematurely actuated leading to insufficient air/fuel. Also, depending on where the piston is in its cycle, both piston and valve/s can try to occupy the same physical space at the same time, which is definitely a bad thing on an interference motor. (On some engines like the old volvo 4 banger, the valves would never meet the piston)
You should be able to determine chain condition by checking to see that the crank is at 0deg TDC for cyl 1, and observing the cam's position. Pull the motor through a few times in the proper direction and observer the cam rotating and see where its timing mark ends up relative to the crank's position.
A tooth is a lot to be off by on the crank sprocket (smaller gear, fewer teeth, one tooth represents a larger % of 360 degrees) but less noticeable on the cam side (larger gear, so one tooth is a smaller % of the rotation) due to the way a crank spins at 2x the rate of a cam.
Great news that it is running, but like above, I too believe in checking the settings and starting from even-stevens and not trying to set timing based on cam position.
Good luck!
