I have a list of 23 BM54 P/Ns. I think the first 3 may be round pins. Yours is No.6 so it should be OK for the flat pins but I don't know the other features of the radios. Anyway yours is one of the older ones. Jochen I'm sure knows about the features. Here is my list from a couple of years ago on bimmerboard.

Here is a listings of all Euro type trunk mounted radio P/Ns.