Source: Marty Tippin (firstname.lastname@example.org), r.c.b., 1/31/96
I've used the Wyest german ale (1007), Wyeast Kolsch (???) and BrewTek Kolsch - the german ale was the best so far (but the BrewTek batch is still in the secondary and is looking promising) - the Wyeast Kolsch yeast gave an odd mineral-like flavor that I didn't care for - but that may be closer to the real thing - not having ever tasted an authentic kolsch, I have no idea whether this thing is close or not.
I've had to adapt his recipe, though, to my style - MIller's extraction efficiency runs around 34 points while I only get about 28 or 29 - I didn't know that when I did this one for the first time and consequently, I had to use 1 lb of dry malt extract to get the OG where it needed to be. Here's my recipe in case you're interested.