Holly smokes SF, I was hoping this didn't happen. This is a bummer. :dribble:
IMHO I would NOT rotate the motor at all at this point. An 8mm wrench is huge (I assume it was not the socket, you said wrench), you don't want to have it get lodged and then stuck between the con rod and or counter balance and some other surface, the motor will never move (rotate) then. That wrench is who knows where. At this point if you couldn't fish it out, I'd do a few things in this order:
1) Pray.
2) Try and contact Radio Howie or others that have pulled the motor or rebuilt it to see if it's possible the wrench made it thru to the pan.
3) Start to pull your pan to see if it made it all the way thru. That involves removing the radiator and header (BTW - get new exhaust gaskets or it will leak).
4) If the first 3 don't work.... the motor may have to come out, or start to drop the lower end as it sits, if that's possible from below. Need other experts on the lower end of this puppy.
Good luck keep us posted on this.