This is a photo of the ID plate on my ZF transaxle. The gear ratios seem low to me given the output horsepower of the 289 circa 1967, but I'm hoping someone might have some insight as to why the ratios are as they are and perhaps what the ID numbers mean.
Nothing to do with horsepower. These are the standard ratios for a "street" GT40 fitted with 7.00 x 15in. tyres which have a radius of over 13in. that is: they are very tall by today's standards hence the apparently low ratios. In the day, this gave a quoted top speed of 165mph.
Depends on rear tire dia, 5th gear equates to a 3.569 to 1 ( 4.22 x 0.846 ) which is taller than say a 69 Boss 302 ( 3.9/1 ) for example and low gear works out about the same. Did/does your Lotus run same tire as GT40.