Although the first version in each case is closer to being appropriate, neither is completely correct.
The sentences should be formatted as follows:
"There were more?" asked Wendy.
"He was amazing!" exclaimed Billy.
Although question and exclamation marks normally end a sentence, if they come before a quotation mark in the middle of mixed dialogue where the sentence continues, then the sentence does not actually end and there shouldn't be a capital letter indicating it does.
Therefore, the next word has its initial letter in lowercase. (Unless, of course, it's a proper name or some other word that would have a capital letter regardless of its position in any sentence.)
You may find Beth Hill's blog post "Punctuation in Dialogue" to be useful. It addresses this and similar issues.