Swapping BW55 for AW70?

[DieselScout]

I recently parted out a '93 240 Classic Wagon with a good AW70.

Is it possible/worth swapping the BW55 transmission in an '82 240 D24 for an AW70 out of a gas 240?

My first thought is that it would be quieter on the highway and get better fuel economy. Would this be true?

Is there anything special about the gearing in the BW55 on my diesel compared to a BW55 in a gas car? And as such, would using an AW70 made for a gas car, not be correctly geared for the D24?

Would also have to sort out the mechanical speedometer...
From some quick reading, it loos like the tail housings can be swapped?