I looked up some specs at the Volvo 164 Club of Sweden and came up with this info:
164 Track F&R: 1350mm = 53.15".

Wheels '71-'74: 15x5.5 w/ 40mm +offset = 1.57" x 2 = 3.14"
53.15" + 3.14" = 56.29" hub to hub.

5.5" wheels /2 = 2.75" + 1.57" + .5"(wheel lip?) =4.82" backspacing.

56.29" - ((2x 4.82") = 9.64") = 46.65" inside of wheel to wheel w/ stock wheels.

Weld wheels 15x12": 3.5" or 4.5" backspace (I will guess it's 3.5").

56.29" - ((2x3.5")=7") = 49.29" inside of wheel to wheel w/ 164 axle.
56.29" - ((2x4.5")=9") = 47.29" inside of wheel to wheel w/ 164 axle.

'86 dana 44/CJ wide track with 54.5" hub to hub -7" weld backspacing = 47.5" inside of wheel to wheel.

'86 dana 44/CJ wide track with 54.5" hub to hub -9" weld backspacing = 45.5" inside of wheel to wheel.

I always thought that the 1800 wheels where the same as the 164 wheels, but I sure could be wrong and I belive the track is 1.5" less than the 164's. This would give me 45.15" inside of wheel to wheel to play with.

If my math is not flawed, the jeep dana 44 should work no matter what. Unfortunatly though, this axle usually came with a 2.73 and 3.31 ratio, but the housing will accept a ratio up to 3.73 and has a 5x4 1/2" bolt pattern. They claim that the housing is centered, but does this mean the pinion or center section?

Still too many variables, but it does look more promising and leaves me the option for a V8. This was a partial year only rear end and might be impossible to find in the junk yards which is what I would be counting on.

Of course, If I could find the so called Volvo-1042/dana-44 axle and I could find someone who wanted some used Weld drag wheels, the custom drilled Center lines might also do. If I where to change wheels, I would want 17x9.5's and 17x11's w/ 275/40-17's and 315/35-17 tires.

http://www.jeeptech.com/axle/d44.html