The smaller nut is about a 10mm size, the big one will be about 13mm I think. All of the 302 Explorers have the ring terminals on the trigger wire, I was saying in the mid-90's Ford had a lot before then with spade terminals.
I had bought a starter for my 91 Lincoln, and it came with a ring terminal and short pigtail section to replace the OEM connector. I later(recently) had to replace that starter again, and I put in a spare Explorer starter, they are virtually the same now with the ring terminals.
The starter grounds through the case/transmission.
Go slow on those nuts and bolts, be sure the socket is square before giving it torque. Rounding off bolt corners is no fun, we all forget that sometimes.