Hi Gas Guzzler,
Your B36 is a the large size main frame. Look for either one in red below.
They came on the following New Model guns:
All blue single sixes, .22 and .32 calibers (except the 32 Mag Baby Vaquero style and Bisley 22s & 32s).
All full size Blackhawks (except NM Flat Top Blackhawks, and Bisleys).
Identification Numbers Marked on GRIP FRAMES (not including Super BH, Brass, Birdshead or Bearcat):
BLUE NM:
Large steel = A (in box) XR-3
Large alloy w/o lock marked: Early = NXR3-RED, Late = XRN-3RED. With lock XR & L
Small steel XR3 (Colt size) (cut for indexing pawl system, no extensions into main frame & only 7/16" thick) = A (in box)
Short steel 'Baby" Vaquero .32s = A (in box) XR-3. If ordered as parts = 302 A (in box)
BLUE OM:
Early Colt size alloy to 1962 = XR3
Late, large alloy to 1972 including Old Army alloy and Hawkeye alloy w/wide trigger slot = XR3-RED
Old Army steel 1985 with wide trigger slot = XRN-3
STAINLESS NM:
Large: Earliest = KXR-3, Next = KXR-3 with a separate N, Late = K (in circle) XRN-3
Small XR3 size (cut for indexing pawl system, no extensions into main frame & only 7/16" thick = K (in circle)
Short = KXR-3
STAINLESS Steel Old Army = KXR-3
There are a few dealer exclusive model exceptions. If I missed any someone is bound to correct me.
Rugers that have locks:
Aluminum XR3-RED's with L in the Cat. #. These are starting to show up w/o locks or L in cat #. 8/23/12.
The blue and stainless XR3 (Flattop & New Vaquero).
KXR3 RED, Bisley, blue steel XR3 RED SBH and SBH dragoon do not.