Yessssssssss!!!!!!!!!!! 
Since alk already reported successful 3400 CD/interface adapter card testing for the 5300, I've gone back to test my original concept, which was to hack the first ever 68k 'Book with an internal CD.
The bad news is that it won't boot from, or even mount, the 8.5 install CD or whatever Norton Rev it was that I threw at it. However, the first one I'd grabbed to test was the same pretty, blue and silver Linux CD in all the 1400 CD fit test pics of the MK I Prototype . . . it mounted right off the bat and there's even a lil' pic of its icon on the desktop.
ATM, that's plenty good enough for me! 
Check out the last three pics in this gallery: 5300c/CD_MK_II
The big deal about this successful test is actually that the 3400 CD interface adapter still works at all. After having enough lopped off the end for it to fit into either prototype case it keeps on ticking! Now all that remains is to source or fabricate a standard ATAPI CD Flex-Cable Extension to adjust for the CD housing's new location snuggled "almost" right up against the (unmodded original equipment!) removable main battery.
I'll DEFINITELY be using one of the 5300c/CD prototypes to finish up the TrackBall upgrade of this 190cs with an internal CD hack as well.
MUAHAHAHAHAHAHAAAAAAAAAAA!!!!!!!!!!!!!!!!!!
jt :ebc: