318 hard start when hot

No. No chance. I use a 5/8 box wrench, sometimes I need a short one to get in there. You sure you're on the starter bolt? There's a transmission bolt right above the starter that's the same size socket.
On my 360 Durango I went with my long extension from the front, strung the extension above the motor mount. And ratchet in front of the cross member. I have several long extensions I mostly use for the bell housing bolts when changing a trans. I think the longest one I have is like 36-38" long. I have a couple of them around 22-24" ones too.