I ordered it from Mid America (a little overpriced) and they assured me it
would fit no problem.  WELL, I had the exact problem you said, the cruise
control bracket sits about 1" too low and hit the + top post.  I briefly
considered lopping off the post but then modified the cruise control bracket
instead.  I put a barrel jack on the battery tray sitting on a thin piece of
scrap plywood I had, and a piece of rubber bike innertube over the top of
the jack for grip and to keep it from scratching, then jacked it up until it
was snug.  I then removed the screws holding the computer in there and
folded it up over the valve cover, and removed the computer tray.  Then
while jacking the cruise bracket up, I bent it over on the top to keep the
cruise diaphram in the exact same position... a little jacking, a little
bending.  Ends up working perfect, with about 2" of clearance over the top +
post, and looks like it was built that way.  Oh yeah, and the tray had two
itty bitty pieces of plastic along the edge that had to be knocked off...
not the edge lip you see but little pieces on the inside, invisible once the
battery is sitting in there.  It looks like it was made for a C4 now, can't
even tell it was slightly modified.