Forostar
Ancient Mariner
I expect most of them to sound the same. Still it makes me wonder if that really is so.

I indeed thought of them but skipped the solo albums on purpose. If we would still count them, then they would end high but still would be beaten by Jethro Tull and that other band I hope you guys will guess.How about Kiss?
74-85 if you count the four solo albums.

Even Zappa reached a point toward the end of his career when some albums seemed like he was releasing new material for the sake of having something out there.
If you're really interested, it seems all his albums are free to download: