69 Z28 Crankshaft number

[z28z11]

So do we know what the difference between cranks is?

Improved/enlarged fillet radii on the rod journals, if I remember correctly. Side rod clearance or chamfer may have been altered (to accept the larger radii) as well to strengthen the rotating assembly under severe loads -

Regards,
Steve

[miket1]

I sent Jerry M. my build date info. on this engine, he replied to me  it is very possible to have a 3279 crank carried over and installed in an Oct.5 , 1969 dated DZ engine', and the 68- 69  keyway is the same, so the 1969 style #7708 balancer and timing cover will work for correct timing.
It makes good sense that if the engine factory had a few extra 3279 crankshafts built up they would use them.