I just checked my spare 428 crank (out of a '66 428 T-bird) and it has a square notch cut in the flywheel flange also.

I believe you are right about the half moon cut out on the 352-360 cranks.

Bob
'66 7 Litre, top loader, 3.25 Traction-lock, Sidewinder Intake, SCJ Exhaust
'88 F150 XLT Lariat, 302, 5 speed, 3.08
'99 Ranger, 3.0, 5 speed, 3.73 posi