M-20 with L-78 or L-72 & deep gear -How?

[mssl72]

This topic is something I have been dealing with recently. A lot of questions have come up, some got answered, others created.

The 1966 Finger Tip Facts book and 1966 Motor Vehicle Price Schedules book both have a page with all the "Power Teams" listed. It shows the engine, transmission and rear axle ratio combinations that could be ordered. I'll list a few examples of what it shows. For Full Size Chevrolet and L72, 427/425hp you could order a 4-speed close ratio (M21/22) with 6 different gear ratios ranging from 3.31-4.88's. If you wanted a wide ratio (M20) 4-speed or a Special 3-speed (M13) it lists only 3.31's, nothing else. The 3.31 ratio was considered standard equipment. In 1966 for a Chevelle ordered with an L78, 396/375hp you could order a 4-speed close ratio with 7 different gear ratios ranging from 3.07-4.88's. If you wanted a 4-speed wide ratio or Special 3-speed you had 5 different ratios ranging from 3.07-4.10's. In Chevelles 3.73 was standard equipment. Corvette with L72 shows only close ratio being available with 4 gear ratios ranging from 3.36-4.11's, 3.55's being standard.
So, for example, why could you get a wide ratio 4-speed (M20) and 4.10 posi in a Chevelle and not in Full Size Chevrolet? Why only close ratio in a Corvette? How did Chevrolet decide things like this? I didn't think that the gears you wanted would effect the transmission you could get. I also found that POP's could tell you Muncie, but not which one. You would need a build sheet or window sticker. I don't have anything on the 1967-1969 model years, but I would love to see what was going on in the same books for those years.