I'm contemplating changing the differential ratios on a '66 109, S2a from the standard 4.71 to either a 4.11 or a 4.43.

The engine will be rebuilt so it will be strong, and I will have 235/85 tires (31.7") and an overdrive (Fairey; .78 ratio). This should take the RPMs (with o/d) at 70mph, for example, down from 3132 to 2946 (with the 4.43) or to 2733 (with the 4.11). I do commute in the truck so the highway RPMs matter to me; I also drive around town a lot. And, I don't want to lose the off-road performance; the low range 1st gear overall ratios would change from 40.81 (with the 4.71) to 38.38 (with the 4.43) or 35.61 (with the 4.11).

At this point I'm seeking others' opinions, particularly if you have experience with a similar setup. I can imagine the modest but nice difference on the highway but I have little sense for whether the changes would matter that much off-road, or even around town.

Thanks for any thoughts on this.