['68OrangeSunshine]

The stock harmonic balancer for the 292 is a 2-groove unit. There is also a 3-groove balancer originally for bigger truck applications (40-50-60) that will also bolt up. Some people prefer the heavier balancer for smoother low rpm's. The 250 L6 balancer is too light in mass to work right on the 292.
A few high tech aftermarket balancers exist for the 292, but cost about $300 +.
As far as the timing marks: there was a design shift somewhere along the timeline -- Early L6s use a timing tab at 4'O clock, the later timing tabs are at 10 O'clock. [I suppose this makes it easier to read the timing light while you turn the distributer, since you don't have to jump over to the drivers side to read the timing marks.]
Age and/or over-revving can cause a stock balancer to "spin" and lose its true mark. 5,000 rpm is considered the redline for these engines stock, as they were designed as a lo-rpm hi-torque work engine, and not intended for racing. Not that that's stopping anybody from pushing the limits, performance -wise.
Do check out "Inliners".