6-speed transmission gives you two (count 'em 2) overdrive gears. Or a close ratio direct-5th with overdrive, like the Silva S15 transmission, can be modified to fit Datsun 1200. Just cut the bellhousing and weld on a fragment of A-series bell housing, then machine the input shaft smaller.
S15 modified; A-series bell grafted on. Is only 16kg heavier than a standard 4spd.
- 1st: 3.630
- 2nd: 2.200
- 3rd: 1.543
- 4th: 1.210
- 5th: 1.000
- 6th: 0.767