Long time no post!
Throttle gear blew up in my #1 Hydro Thunder, so rather than drop $30 on a new one with the same physical design problem, I designed a replacement part and printed it.
I've put the files out for free over on Thingiverse:
https://www.thingiverse.com/thing:6874028
Going to mirror lilypad19, get the Shoestring test rom. It's pretty robust and will even spit out some graphical error codes when the board won't fully boot.
Some CF Cards correctly identify the IDE Transfer modes they support, some don't. This is why I like using the IDE Disk-on-module/SSD's instead as they have explicit support for correctly identifying themselves.
Exotica U3 should be 27C322 (4096kb). You'll have to use something like HJSplit or Goetz File Splitter (now free - http://www.lawrencegoetz.com/programs/gfsplit.htm) to bust up the ROM into sequential parts.
I pulled a copy of the Fujitsu MB8516 datasheet. Says (in Japanese) it's an equivalent to Intel 2716, so yep, that would be correct, any regular (non-TMS2716) will work here.
The link from Marcos is all regular 2716-equivalent parts. Should be the same size.