Only you can confirm what your own ignition timing is. I would have said 24 but I've never even owned a non-hemi. I'm sure I didn't spend very much on the cheap timing light I have, but you don't need a timing light unless you NEED to be very specific. All you need is a degree wheel (which you can print for free and stick to some cardboard). After finding top dead center, you can turn the flywheel to its firing position. You can use a piston stop to find top dead center, but you can probably eyeball where TDC is +/- 1.5 degree just by looking at the piston move through the spark plug hole while you rock the flywheel back and forth.
Without a timing light, set the flywheel magnet about where it is in the picture. That is about the firing point. The leading edge of the magnet is centered under the upper leg of the coil and the trailing edge of the magnet has just passed the lower leg of the coil.
Eyeball method will only give you +/- 2.5 degrees at best. But it will tell you 26 +/-2 degrees or 23 +/-2 or 20 +/2 degrees. And if you measure a bunch of times and take an average, your +/- 2 degrees becomes much smaller.
With a piston stop, you can probably get closer to +/- 1.5 degree.
If you NEED to know better than +/- 1.5 degree, then you probably need a piston stop and a timing light. And even with a timing light, your accuracy depends on how thin of a line you can draw and how well you can draw a corresponding line while the engine is running and you are holding the timing light in your other hand. I imagine people with plenty of experience can only get about +/- 0.5 degrees.
BTW, ARC's Honda, Clone, and Predator flywheels are set at 32 degrees. This is accomplished by offsetting the keyway 8 degrees. They describe their older flywheels with straight up keyways as 24 degree flywheels.
