I would like to get a bit better educated on the different rear axles used in PVs over the years. Questions as follows:

1) I understand there was a 4.56 ratio axle used on earlier models, and later versions had a 4.10 (?). Does the change in ratio accompany the change from B-16 to B-18 engine? Was that late 1960/61?

2) I've seen some views from an on-line parts book (written in Sweedish-I don't read Sweedish), and it apears that these were quite different in design: the differential on the earlier one (higher numeric ratio) removes from the front, the latter from the aft. Do I have this right?

3) I've read about rear axle swaps...120s, P1800s, 140s, even one from a Ford. This is where I really loose it. I guess I'm mostly curious about commonality of parts here, not really interested in changing from drums to discs.

4) If the 120s & P1800s were heavier than a PV, and were equiped from the factory with a B18 & overdrive, I would think a standard B18/OD in a PV would work nicely as long as the rear axle ratios were common with the 120s/P1800. Or would the higher numeric ratio rear axle coupled to an OD offer better flexibility by yielding a snappier response in town & an adequate cruising gear for the highway?

Long story short-what's the desired rear axle (with respect to ratio/driveability/supportability) to use in a PV with a stock B18 & OD?

Thanks in advance for the enlightenment!

Joe in St Louis