Searching for information on CS rim and tire combinations about 4 years ago from other coupe owners on the net, this is what was reported back:
[Thanks again to the people below for their assistance!]

16" rims:
Lance:
16x7 front with 205/55R16
16x8 rear with 225/50R16

Tim:
16x7.5 front with 205/55R16
16x8 rear with 225/50R16

in 14" rims:
Bryce:
'69 2800/3.0cs uses 225/60R14

Jim:
215/60R14 front
225/60R14 rear - rubs when bottoming out

FWIW:
I had recorded  at the time some the combinations that were thought to be possible and what the effect was on indicated road speed:
(rim width)
(tire size/profile), (Percentage difference from stock circumference), (speedometer indicated road speed vs. actual speed)

14"
195/70,   0.0%,    60.00 mph indicated road speed
205/70, 2.23%, 58.69 mph " " " = 60 mph actual
215/60, -2.39%, 61.47 mph
225/60, -0.48. 60.29 mph

15"
205/60, -0.25%, 60.15 mph
205/65, 3.01%, 58.25 mph
215/60, 1.65%, 59.02 mph

16"
205/55, 0.52%, 59.69 mph
225/50, 0.45%, 59.73 mph

Recently,
I have seen a web page guestbook entry where there was some info posted a few years ago at:
http://www.geocities.com/MotorCity/Downs/7274/geobook.html
 

  Scott McClenahan - 06/19/99  00:51:16
  My Email:scottm@tdl.com  [no longer valid. wb]
  Model: 3.0 CSL  Year: 1972  Color: Golf
  Engine: 3453 inj & 3.0 carb
  Shoe Size: 225/16 & 245/16 on
  Alpina
  Favorite Fish: Alpina
Comments:Nice Site! Owned 15 yrs, found car in 
Milan. 112th of 160 carb prototypes built in 1972.
 VIN #2212260. BMWCCA Instructor car commonly 
seen at Schools on West Coast.
 (Please attend CCA Schools!!!) Undergoing
  thorough resto 6-99. ("Surprised" that the
 prototype V N #'s are still listed as CS's on this
 sight.) P.S. I'm looking for a clean set of orig.
 14x7 Alpina Rims. (Mine were "borrowed" by
  someone while in storage...)

I hope this helps somewhat.
I had written to Scott but the e-mail address is too old. Perhaps there will be more info available on the tire profile series above or any rubbing and/or fender rolling if he could be contacted or if others have gone that route.

I  too am interested in finding out what tires will fit the 16" rims and what works best for track sessions or in general. I have acquired some Fittipaldi 'mono star' 16" rims (8"wide) from a parted out 635i and am waiting on a set of  some half used 225/50 + 245/50 Yoko's from a wrecked Porsche 928 I had found at an auto recyclers.
I'm not adverse to rolling the fenders a  bit anymore and figure this might be necessary with such a wide tire in the rear.

My rational for considering such a large tire in the rear is the planned installation of a Korman triple Weber 40 DCOE induction setup acquired from the same rusted six series along with the Fitti's.
I'm wondering if such a large tire be necessary with this setup? I will be using the stock cam at first with expected power output said to be around 240 HP. Any and all help is appreciated.
TIA.

Bill Boyd
'74 3.0CS