[Dan Case]

Case Material
Between SAI and Mr. Roush’s research the mystery time frame is roughly between when “iron” CSX2115 was completed (June 1963) and “aluminum” CSX2136-2138 (about August 1963). From your first post today I don’t think CSX2126 would be in the discussion because it was finished at AC Cars before CSX2080. Circa early February 1963 CSX2126 was a running car.

Gears
I just called Dick Roush. Dick has helped find parts and coordinate shop work of many Cobra owners repairing or rebuilding their original transmissions. As far as he recalled:

B sets = only in the iron cased Galaxie transmissions that happened to get redirected to new Cobras

J sets = he does not recall finding a J set in a genuine Cobra transmission, he allowed that it could have been possible but doesn’t recall any.

L (high nickel) sets = aluminum cased Cobra transmissions

K (high nickel) sets = aluminum cased Cobra transmissions introduced sometime in the CSX22xx range, example he knows CSX2246 had a K set originally, my black car CSX2310 was fitted with a K set.

M (high nickel) sets = aluminum cased Cobra transmissions introduced sometime in the CSX23xx range, his belief was that the later the chassis was the more likely it was fitted with a M set.

The tough part to deal with is chassis were not finished in order so it is meanless to think that since car CSX2xxx was fitted with "such and such" that chassis CSX2xxx±1 or 2 or whatever got the same part or assembly. Case in point AC Cars wise CSX2126 was finished at AC before CSX2080 was completed at AC. CSX2126 was rushed to SAI ahead of other chassis so even at SAI it was running much earlier than any other cars numercialy close to it.