Essbos;104817 wrote
My 3.73 and 4.56 out of a 144(74 model with b20e+BW35) and 142(67 model with B18b+m41) must have been options.
Interesting! That was either a special order, or somebody put a 164 diff in it. Does your car have any Special numbers on the ID plate which are different to this?

(This plate is on my 1974 145, with B20E and BW35. The book doesn't list whatever special options S-6168, S-6261, S-6263, or S-6265 actually are, so any info on them is welcome).
The book says that in a 74 model, you either got a 3.9:1, a 4.1:1, or a 4.3:1 from the factory.
See parts book, Grupp 4, page 76.
http://weblisher.textalk.se/gcp/20160126-006/paper.pdf
You're right to pull me up, the B18 car is a different story, my statement was somewhat overbroad and should have been "
73 and 74 model 140s
in Australia never got 3.73s as standard AFAIK, only 4.1:1 and 4.3:1".