Punctuation Question?

"Joe won," he said,"I thought he was the best runner."
"Joe won," he said."I thought he was the best runner."
"joe won." He said,"I thought he was the best runner."

which is correct? I am studying GED now, so maybe that's a strange question.

The first two are correct. The third is incorrect because Joe should be capitalized (if it were, then it would be correct also). The differences are in style only.

"Joe won," he said,"I thought he was the best runner."
"Joe won," he said."I thought he was the best runner."

Re No 3
"Joe won." He said,"I thought he was the best runner."

re first one - where does "he said" belong to?

Should be
"Joe won", he said; "I thought he was the best runner."

or

"Joe won"; he said, "I thought he was the best runner."