Hi Bob, can't help with the bumperettes but I know a couple of differences between sedan versus C/C seats. C/C seats I have seen have four rows of pleats whereas sedan seats are typically five rows of pleats. Additionally, C/C seatbacks can be folded forward to enable passenger access to back seat (after unlocking) whereas sedan seatbacks do not have this feature.
I also believe but can't confirm that 3.5 seats are slightly narrower than earlier C/C versions - maybe someone with more knowledge can check in on this. 3.5 seats most likely have provision for headrests and I believe that the hinge covers (and possibly hinges) differ from earlier C/C versions. Lee