Original source material taken from the following post:
http://www.r3vlimited.com/board/showthread.php?t=154876
With a couple swaps I’ll be doing I’m attaching the m20 C101 engine side connector to m50 family wiring harness, and while there is a lot of information about this scatter around this and other forums it can be hard to find for some people. So I’m making a bit of a guide with some of my own experience advice for everyone to enjoy.
Pins:
You’re gonna need from your local or online dealer
- 20 x 61-13-1-376-191 (Only really need about 16, 20 allow for mistakes)
- 2 x 61-13-1-376-193 (for larger gauge wire if you want)
- 2 x 61-13-1-376-195 (for larger gauge wire if you want)
- 1 x 12-52-1-707-283 (C101 Black Plastic Connector)
The last two numbers are required but i just like using the larger connectors for the larger gauge wire just in case
NOTE: You can order pin’s from Tischer (getbmwparts.com) it’ll say the part is superseded but this is not correct, just make sure you put in your notes to them that you actually want the part number 61-13-1-376-191 Otherwise you’re going to be sent the pin with a flying lead attached.
I’ve brought it to their attention that they’re catalog is incorrect…so hopefully they will change it.
Crimper’s:
Pretty much all the crimpers that are for sale anywhere are not meant for these style of connection found on our cars. You can get them from the dealer but i didn’t even bother to find the price. But I have found one place that does sell very similar ones…
http://www.vintageconnections.com/
These guys in the PNW sell the best crimper’s for the job, hands down, they are ratcheting insuring a proper crimp and you can also buy extra dies for the crimper to allow you to use them in other applications. I highly suggest you use these over anything else, they’ll ensure you get your wiring job done right.
Also a misconception with crimping is that soldering is done after, but thats not the case! You should only solder crimp joints that are loose.
Pin Removal Tool:
Unless you feel the need to purchase the $80 Pin removal tool from BMW, I found a cheap and easy solution. 
RCA Coaxial “F” Connectors for Coaxial Cable RG59 Part Number VH65
I got mine at home depot for $3.99 I’m sure they sell them online as well. A quick search revealed a bunch of sellers. 
These fit over the pins perfectly and in to the plastic connector well. They’re tad tight so i took a dremel and sanded down the outside a tad to get rid of the ribs on the connector, and it fits perfectly now.
Also remember if the wire won’t come out, that the black plastic connector does spin and lock them all into place, just bend back 2 small tabs on the back and spin it counter clockwise. You’ll understand when you see it!
Conclusion:
After you gather all your parts and tools, the act of putting on the pin’s is pretty simple.
- Create a chart labeling what wires from the X20 Connector go to corresponding pin hole on the C101
- Cut the old X20 Connector off the m50/s50 family engine harness
- Remove all the rubber coverings as you deem necessary, it depends if you’re using the m42 wiring harness cover or the e36 one.
- Identify the wires you will need, strip back the ones you will use.
- Tape Off/Shrink Wrap The wires you won’t use.
- Crimp on the pins on each wire you will be using, use the larger pins for the 2 or 3 larger gauges wires (If you bought those pins)
- Insert the pins into correct pin holes the new C101 Black Connector You Bought.
- Plug the new created C101 Connection into the main harness on your e30.
There are lists all over for pin outs + connectors, I’m not going to post mine until i feel safe/confident with it 
But you can make your own using the ETM Manuals found here.
http://wedophones.com/BMWManualsLead.htm
Additional notes:
The proper pin removal too is 83 30 0 495 385
you’ve inspired me… Made my own tool from brass fittings.
