Grind off that wrench end and weld on a T-handle, nice iron draw pin.

I don't recall ever seeing mushroomed peg heads. But I have seen clientele drive a peg with a sledge hammer....... the draw was tight..... the peg sharp.... it went in right but was driven out the side of the timber! after making it through the tenon the peg was pushed off alignment. I heard way to much pounding and came to look. Always entertaining to have extra "help".