I took a few pics of mine, with a shot of the oil pan.
It's a 4-stepped pan, but I don't see a removeable base plate.
http://good-times.webshots.com/album/560430195hzVgsx


1968 pro-touring twin turbo Camaro
1968 Chevy Longhorn truck-soon to be Cummins powered
1963 GMC Twin-Six V12 engine
My Twin-Six page:
http://good-times.webshots.com/album/560430195hzVgsx