According to the wire table 310-16 ( 99 Code Book, I don't have my new book with me) # 8 wire is good for 50 amps in the 75 degree column, and I know this is good only if the terminals are rated 75 degrees, which they are. Does
8/3 with ground romex qualify for this rating also? I had an inspector tell me once that it didn't, but I can't find where he would have got that from unless it was in an old code at the time. Thanks, Steve...

He is maybe refering to 334.80, which limits the ampacity of NM cables to that of the 60 degree column.

Yup that is what he is talking about and you can't get away with the "round up" trick you can with #6 since 40 is a standard breaker size. Even if you decide to go for SE/SER you still can't use the 75c column because of 338.10(B)(4)

Hi Greg,
I could be wrong, but I thought 338.10(B)4 excluded 334.80 Ampacity.

You are right. I should try to read a little better before I speak. My original thought was that it was OK, then I looked it up.