My E34 loom does not coonect upto the E30 loom

[Tims07]

Got all the oils bits from a 1988 E34 535SE and they are going into a 1986 cabby that was originlly a 325 auto, but had had a 2.7 conversion done.

So am I being incredibly dense (which is always more than likely) or is there a difference in the loom connectors?

Also found a 65751381287 in there, above the under dash mounted ecu, which does not seem to be listed on real oem. As far as I can work out this is an old alarm type thing? I presume leave well alone

[gareth]

the C101 plug (engine loom to car loom connector, on the bulkhead) was different on earlier E30's.
what shape is it?