Measure old transmission. Measure new transmission. Subtract the former from the latter. Take your driveline to a driveline repair shop and have the front half shortened by the difference in length between the old and new trans. Get it balanced, and while you're at it have them install greasable, replacable u-joints. Hand over $400, live happily ever after.
You are also going to need a new yoke for the front of the driveshaft. This is the part that bolts to the rubber guibo joint. Since 320i 5 speeds came with either 3- or 4-bolt yokes, you'll need one that corresponds to what your 5 speed has. Basically, you need the front part of the type driveshaft that came with the 5 speed. The driveline repair shop will have to cut the yoke from the 320i driveshaft part and weld that into the 2000CS driveshaft.
2000CS 4 speeds have the same arrangement and I am going through this with putting a 5 speed in my 67 car, VIN 1106416.
My driveline shop suggested a doner driveline out of, I believe a 318i, it has a splined shaft portion that will come in handy to take up any small errors in measuring.
Also be sure to see if your center bearing carrier is the newer style, or the "ruth goldberg" contraption. Mine was the later, it's a complicated setup with springs. I decided that when I end up installing the 5 speed, I was going to weld in hangers on the tunnel for the later style. From what I can gather, this style was introduced sometime in '67, although I'm not certain. Hopefully yours has the later style.
Thanks mark i think the 318 i drive shaft will worf perfect fit just have to cut about 1 inch off of the thing Me and my buddie were thinking the same thing yesterday as i was trying to take the tranny out