Yes the "bowel" that the blades bolt to I am calling the stump jumper.

I have found no shear pin in the shaft that the pto driveshaft hooks
to, I had the cover of the gearbox off. The gear that is on the shaft
that goes down to the blades had some teeth that were a little bit
chipped.

Thing is, the blades spin fine until I get into the grass, then it is
like they dont spin fast enough.

Is there a key or pin underneath ? Where would it be?

The large nut attached to the bolt underneat the bushhog is spot welded
to the bolt? WOnder why?