Forgot to mention that the 4-cyl cooling system (including factory electric cooling fan) won't fit with the M52. So I surrendered and installed a new 6-cyl system from Pelican & some pieces from Coast BMW here in SLO. These components include a new Behr radiator, new 6-cyl fan shroud, new overflow container, hoses, mounts, etc. In total, this added $500 to the project.
I am going the "Fan Delete Mod" to avoid another mechanical plastic fan failure (which I was "blessed" with on my 328i a few years ago
). I used the 318ti temp sensor (80*C low and 88*C high) in the 6-cyl radiator, and wired the A/C auxiliary fan out of a 325i to come on at those two temps. Of course, I used BMW coolant and added two bottles of Redline Water Wetter. Fingers crossed it'll work as many other 6-cyl guys swear by (and some apparently swear at!).