Sunny (B310) came with the H150 diff. 1200 utes came with the H165.

Keep in mind that an A15 does not need overdrive, it can run at 4000 RPM all day long with no worries. But for better fuel economy and less noise, either fit the 5-speed OR a lower diff ratio. If you have the 3.900 ratio now, a 3.700 will lower the RPMs on the highway, at the expense of slightly slower acceleration. A14s here came with as low as 3.54 ratio, which were slow as a dog taking off, but got very good fuel economy.

Keeping the higher ratio (4.11 is superb) along with 5-speed overdrive is the most flexible combination, but costs a a lot for the 5-speed. A good 4-speed is only $50.

I run 4.11 with a 4-speed, and have gone on two 1000-mile trips cruising at 120kph.